Getting over infidelity

So this is my first post on here even though I've had the app for a while. I've googled advice on this topic almost every day for the last year and finally am just going to write out my own experience to see if that can help me finally find some healing.

I have been with my partner for a little over 3 years now. The first year was really rocky as we both had just gotten out of long term relationships and I don't think either one of us was planning on getting in another so soon. As these things go, you can't control when you meet someone you bond with. We both said/did some things we regret in the beginning but as we were very on and off those days we're easy to put behind us once we both made the decision to actually try to be together.

Almost exactly a year ago I thought we were in a good place (as good as you can be when both parties deal with mental health issues) until I decided to look through his phone and found him talking to another person. This was the first time I had ever looked through his phone so I was pretty blind sighted by this. I found him talking to a "family friend" who was sending him inappropriate pictures and they were even saying they loved each other. We battled for his phone for a couple minutes which just led to me leaving and breaking up with him.

To my surprise, after I left I received a phone call from the police asking me to go back to my partner's apartment because the neighbor had called about yelling. In CA, whenever there is a call for any type of domestic dispute they have to arrest someone in order to "separate the couple". Even though I had already tried doing this myself, somehow I was the one arrested. This day ended up being the most traumatic day of my adult life. As I sat in the jail holding cell officers just kept walking up telling me they hope I wouldn't go back to him and that this taught me a lesson. My best friend bailed me out within hours and after hiring an expensive lawyer my arrest was reduced to a detainment (as it should have).

We ended up back together. I sought out therapy to help cope with the events that had just taken place but was quickly discouraged when the prescription I was given made me feel horrible. My partner and I did an online couples therapy seminar which gave me hope. We even ended up moving in together and have now lived together for several months. While our relationship has gotten better and we do love each other, I have had a really really hard time moving on and trusting him. I have nightmares every night almost that he is cheating on me, with the girl he talked to, with someone new, with men... in every way imaginable. The dreams are so vivid they make me wake up in a horrible mental state.

Point is, I want to move on. I really do. I want to be able to trust him again and enjoy the good times without worrying there's something else around the corner that will blindside me again. I just don't know how. I have tried so many different forms of self care and have actually made really good strides in my personal life but I can't let go of my anxiety long enough to enjoy any of it.

I appreciate anyone who is taking the time to read this long cry for help. If anyone has any advice on how to heal either myself or my relationship I appreciate it greatly. I just want this heavy weight off of my shoulders. It has been wearing on me for so long already.