Help-I believe I’m in very narcissistic relationship.

Hello everyone, this is my first post.
I’ve been in a relationship going on three years. A quick background of me/scenerio:

For starters, my girlfriend is on disability (chronic pain, brain fog, adrenaline dumps, sometimes uses wrong words, in constant (fight or flight from the physical illness).and deals with much financial struggles - due to recent loss of child support. It’s gotten worse to where she literally can’t figure out how she’s going to pay next month’s bills and moving forward (her car was just totaled by an act of nature and she hardly got anything and has no idea how she’s gonna get a car. On top of that, she has to pay half her daughter’s semester college tuition and she’s also trying to figure that out so with her illness and how it causes fight or flight (so add this stress of life on top of her illnesses) I’m sharing only to see if this helps in giving you a background on her current situation into how I am being treated and have been treated for quite some time. 

Early on our relationship as we were getting to know each other, we shared a lot of things both of us. There’s been several occasions where I refered back to our previous conversations and said hey remember that, that explains why you like such and such (could be about male preference or other topics not a big deal I shared the same). To give an example, we were talking about her previous marriage and how her ex-husband cheated on her. Several months later, she mentioned that he divorced her cause he thought she was acting inappropriate so I asked her what she meant by inappropriate as she stated earlier he had cheated.
She got very angry at me And said she never use the word inappropriate - ex Husband divorced her because he claimed she was cheating on him however he’s from a strict ethnic background to not believe in divorce so I was told that he accused her of that to move forward with the process.
She stated he was the one cheating on her and her daughter at one point was talking about her father and mentioned she had cheated on her mom/my girlfriend.

So after she said inappropriate (100% certain she did), which is not a big deal cause he was accusing her of cheating which is inappropriate, She got mad hung up on me and I didn’t hear from her for a week until she completed moving her daughter into college (there were a lot of stressful things going on her life, so I’m not sure if I’m making excuses for her) (as I said above, she ghosted me for just over a week a quick background on myself. I have bad PTSD from my girlfriend in high school who was kidnapped and then sadly died unexpectedly a year later. Because of the Unknown of not knowing where she was etc (my friend x in HS kidnapping), I panic if I don’t know where my children are if can’t get in touch with them along with other people I love. As I said, she knows this and to ghost me like this, put me in one week of severe PTSD. Since then, she has ghosted me a couple other times and has apologized, saying she was acting like a brat.
Over the course of our relationship, there’s been a handful of instances where she said things in the past and she says I never said that that’s not something I would say. Up until very recently I’ve been giving her the benefit for it out and thinking maybe it’s me misinterpreting or miss hearing things.

On another note a few years ago, she was in a serious relationship and her boyfriend of two years cheated on her, which apparently devastated her to a horrible mental state. I do know this to be a fact so she has PTSD according to her from her ex-husband cheating on her as well as her last boyfriend.
Personally, I feel I do everything in my power to put her mind at ease that I would not do that to her ever or anyone I was dating - as she questions me where I was what I was doing, etc. I’m sensitive to the fact that on a guy’s weekend I went back to the hotel versus going out after dinner to bars, cause I know she would be very concerned and worry.

I was raised when you hurt someone’s feelings, regardless if you don’t think it was a big deal, you apologize and be more sensitive to them and take ownership.
In most occasions, she doesn’t take ownership and sometimes doesn’t apologize. 

Like above when I told you, I give her all the reassurance (frequently) I can give that I would not cheat as well as stay in versus going out with friends. I do not get the same thing in return regarding one or two items, I’m insecure about that was done in the past - she says “we already talked about this and loses patience. she’s very short about it, which I don’t understand because I give her all the explanations she needs so I can take that anxiety away from her. 

A couple of examples that happened early on, a week before I was to fly up and see her she had mentioned she wanted me to meet her dad. So the night before my flight was to leave. I asked her what day we’re going to meet her dad and she said I never said that - I said yes you did. I stood firm and almost canceled the trip because I didn’t wanna get in to a relationship 12 years after my divorce which this would be the first relationship with someone who would lie so early on. Long story, short, I flew to see her in one of the first things she said to me, was I apologize for lying.

One last scenario which really crushed me, three months and I was so happy to be with someone and in love again. It’s been 12 years since I felt like this again- I bought her a couple pieces of jewelry to signify our relationship and love, etc. Due to her illness, she was seeing a physical therapist for a few years (he’s married, not romantically), and he complimented her T-shirt, which is something I gave her as my son got a scholarship at a good sports college, which people recognize. He asked her where she got the T-shirt and she said a close friend gave it to me. She told me she shared this because she felt bad that she used the wrong Word and felt she needed to tell me. It absolutely crushed me- I know it might be petty to feel crushed over that, but it just had been so long and nobody has ever done something like that to me. I.e. referred to me as a good friend not a boyfriend. I think one of the reasons it bothered me so bad cause her daughter a couple months prior jokingly said oh mom I think you have a crush on him cause she was mentioning something that he helped her with ( physical therapy wise).

There are a lot of other instances, I could share, one being that every now and then due to her illness and she gets two hours sleep at night and all the stress if we have a disagreement or argument, she breaks up with me and I have to talk her back in saying you’re tired It’s an impulsive statement - she listens.

I really feel like I’ve turned in to a weak man because I never would’ve put up with this.
I never heard of the word gaslighting until a month ago making someone feel like they’re crazy not remembering certain things and that’s when this really got me thinking. 

Lastly, as I said, there’s several other instances, I could share similar. Please know, I am very far from perfect and I’ve done things that could be narcissistic as well, but it’s not a constant theme. It’s instances which I’m not proud of and I brought up with my therapist cause I’m concerned I don’t wanna be like that assuming I am.

Another sidenote, which might be beneficial, 
I was so lonely after my divorce and I’m scared of ending this because I will be drastically lonely - i’m a very sensitive guy and cry easily, as I wear my emotions on my sleeve (I ball my eyes out if an animal dies in a movie - at the same time very tough if needed).
12 years ago when my ex and I divorced, she wanted to move far away to where she grew up to be near her parents - I said OK because I didn’t want our children being interviewed by lawyers and judges, so I raised enough money to move down and live close to my kids (a town over) and eventually find a job. It was very lonely, not knowing anybody and even currently the friends I have are all married and rarely can get out so I spend my time here alone and don’t wanna go out alone at night.

Thank you all so much for reading this. I’m very grateful - I did a Google search to find this forum cause I don’t know what to do.
I know this is long, but there actually is a lot of things like I said I had to leave out.
I would love any advice all you guys have
Thank you again so much (also, I battle severe depression and anxiety).

An important piece, since we’ve been dating every now and then, I will see her looking at other men in a couple times she smiled. This is also new to me and find it very upsetting because I would not disrespect somebody I was dating or married to and do something like that.