<human>: Condense the text into a few key points

Hi, guys. Details are in the title.. I dated this girl off and on for 7 years. We were high school sweethearts, then went to both college and graduate school together. Were very serious, lived together for 2-1/2 years, talked seriously about marriage and kids. She broke up with me about 4 weeks in to her studying abroad. I helped her mom and brother move all of her stuff out while she as still in Europe. 

 I think the break up was a good idea, rationally, but it's really affecting my performance in school. I cry about it almost every time I drink (which is about once a week with friends). It distracts me during class. I've had ups and downs with it.

However, one of my good friends who I hung out with all Summer just came over to my house. He was one of the first people I talked to about the break up. He was mutual friends with both of us. I always suspected my girlfriend had a thing for him, but she promised me she didn't at all. Well he just told me they've been sleeping together and he wanted to tell me to my face. 

I feel like lightning just struck in my chest. It's spreading. I feel like my elbows and knees are weak. I almost just threw up. 

I can't say I'm not mad, but the rational side of me isn't angry at either of them. We're not dating, so she's not cheating on me. However, I feel so violated. I shared so many intimate details of our relationship with him.. and I talked so much about the break up with him. I want to just do whatever is the most mature and emotionally healthy thing in this situation. Right now, I'm going to go work out, then come home and try and finish cleaning my room. I would love to hear from people that have been in similar situations.. Any advice, reddit?
<bot>: girlfriend of 7 years broke up with me and I just found out she's banging one of my good friends. How should I best deal with this and move on? Anybody out there been through something similar?