I (27M) tried to forgive her (30F) for cheating, but it wasn't working.

I was in a 6 month relationship with a girl I grew to be best friends with. Everything was fantastic for a while and genuinely wanted to be with her forever, but her deep psychological issues started surfacing in the last month and she would be depressed/mean randomly. Everything about our relationship suffered, though I never wavered in loving her & wanting to ride out the storm together. These issues culminated in her breaking up with me twice and then asking me to get back together the same or next day. I took her back, of course, but said that the third strike would be the final one and that she needed counseling.

A week or two later we went to a wedding on Easter Sunday and she was cold physically and emotionally towards me the entire day. Not exactly how people normally act at a wedding. That pattern seemed familiar so I drew the line there and broke up with her the next day. I have a lot of pride -- I didn't want to be someone with who was going to treat me like dirt for no reason. I cut off contact from Facebook, Instagram, calls, texts, and started the tough breakup recovery process. A week later she gets in touch with me via GTalk and says loves, adores and misses me, and wants to come over to tell me some bad news. I thought she was pregnant. @*$#. Stomach dropped, but nope...that wasn't it.

Turns out she cheated on me the Friday before Easter. Lied to me about going home, got pissy drunk at a bar, went home with some random guy and slept with him. I was (and am) extremely devastated. I'm very traditional when it comes to trust and loyalty and this was a deliberate attack on my values. At the same time, I felt glad that she was at my house and still had feelings for me, so I heard her out after the initial "get the fuck out!" shock reaction. The reason she told me of her cheating a week after the fact was to try and salvage the relationship. She felt like she realized all the harm she was doing to herself and others and snapped out of it and wanted to come clean. Acting on emotion, I said I would try to give it a shot and wrote a list of things she had to do to regain my trust. She ended up staying over, having a few drinks, and we had sex & cuddled. I was in gut-wrenching agony (literally dry heaving) all night.

That agony continued for 2 more days. I could barely eat or get out of bed. I constantly felt sick at the thought of her and another guy hooking up. It was looping in my head over and over. Anyone who has been cheated on can relate. I dropped 5 lbs just like that. I saw her again and she was making an honest effort to make things better by checking on me frequently and planning out future travels and events. Let me tell you, all the reassurances in the world aren't enough when there isn't trust. I do believe it was a one-time deal and that she was willing to make changes, but deep down I knew it wouldn't be the same. I am hanging onto a memory of her. I'll always have the mental image and words "I went home with someone..." burned into memory.

I told her today that I am not myself right now (normally a cheery, confident person) and there's no way I can try to fix this relationship until I've forgiven her. It's not fair to either of us. I did leave the door open with a "if it's meant to be..." line and said that I hope she sorts her life out, but I feel like with time I will just move on. I deserve better.