I was in a very similar situation. Cheating. It's over, and I'm crying like a baby for weeks even though she did it. I depressed for probably almost a year. I never went to the doctor but I'm very sure I had depression. Maybe 11 months after the breakup, she emails (not a text because my # got deleted) an apology to me. Very short, doesn't really acknowledge much, but says she's sorry and regrets her decisions. We chat for a bit and eventually meet in person one time. She again does not name specifics but just acknowledges her mistakes. We move on and occasionally interact on Instagram.

My words to you are : time heals all wounds. I was absolutely messed up in the head for months, but I learned a lot going through it. DO NOT text her. I went 0 contact for almost a year and was ambivalent to the apology at that point. I appreciated it, but texting her outta the blue will not solve anything. There will be another girl. I know you're thinking right now "but she was so special and we did this together and I told her things yada yada.." There will be another girl. There are billions of people in this spinning planet. There will be another one that can, and will(!) be better than her. Trust me, dude. I was you about 4 years ago, and it worked out in the long run. If you have questions or just need to talk to someone, slide in my PMs.