I need some relationship advice

I've been struggling a lot with my relationship and I genuinely don't know what the right thing to do is anymore. My partner and I have been together for 11 years, and we've been in a romantic relationship for the last 4. I used to love her deeply, but over the past few months i started to lose those feelings, and this caused me depression, anxiety, and a complete loss of appetite, I don't have the energy to talk or spend as much time together as I used to, and even though she's been patient and supportive, I know the distance has hurt her, I keep finding myself drifting away from her.

I used to be head over heels for her for 3 years and im not saying it’s been all good or all bad. 

Every time we argued or had a fight i feel like she isn’t listening to me, instead i feel like she was trying to prove something and not understanding me.

She disappears a lot and I always found myself seeking her affection and time to spend together and talk and it really hurts how im basically begging for my needs in this relationship.

I spend nights and nights talking with my friend about how i was struggling with this and they kept telling me to be patient and communicate and i did, a lot. But nothing happened and nothing changed all i got from it is me apologising.

A year ago i met a friend on some game (i was feeling lonely at the time and tried to have some company and distract myself) i didn’t think much of it but then we started to talk and spend time together more and more until we got super close but nothing crossed the boundaries. 

At this year i felt loved and understood and listened to, he gave me what my girlfriend couldn’t give and loved me the way i wanted to be loved. And then i started to feel like i don’t love my girlfriend anymore.

I never intended for it to happen, and I felt an overwhelming amount of guilt because of it. My partner knows about my feelings i told them about how im falling out of love because i didn’t wanna keep things away from her, and after many emotional conversations she told me that I don't have to choose between them and that she doesn't want to lose me. Even with that reassurance, I'm still left feeling confused, guilty, and emotionally exhausted. Sometimes I wonder if I'm staying because I truly want to, because we've been together for so long, or because I'm afraid of hurting her. Other times I can't imagine my life without her and the thought of leaving makes me feel empty.

I don't know if what I'm feeling is because my mental health is making it hard to connect with anyone, or if it's a sign that our relationship has changed. I don't want to make a decision I'll regret—whether that's ending the relationship or staying in it for the wrong reasons. I care deeply about both people involved, and the last thing I want is to hurt anyone.