SUBREDDIT: r/relationships
TITLE: Breakups: Me [21 M] with my ex [21 F] 2 years, How do I deal with anxiety from seeing my ex?
POST: I broke up with her at the end of last semester after exams due to the overall stress of my life coupled with the stress and taxation she brought on me. I never really felt physically desired, yet I felt absolutely emotionally drained most of the time, and even when she began to be less emotionally needy, I still felt resentment about being with her. I didn't feel comfortable being with someone more than two years if I wasn't absolutely sure I wanted to go all the way with them and that was definitely the case, especially since she was my first girlfriend and the first girl I ever had sex with.

It's taken the entirety of the summer for me to cope with the feelings of guilt and detachment from breaking up with her, even through I know I shouldn't feel any guilt about doing what I think is right. I thought I was fine after last week when I had a decent hookup with a girl in my classes and she pretty much outshone my ex physically in every way.

Unfortunately, during work, she came to my store and I even rang up her items, and the entire exchange almost gave me an anxiety attack and prevented me from working at full capacity for the rest of the night. I even tried texting the girl I hooked up with out of desperation but she didn't even respond back, which made my anxiety worse. 

I've felt like shit this whole summer and I have no idea how to cope with it. I've felt that I've had enough self-respect not to go crawling back to her after breaking her, well, both of our hearts, but I feel lost as fuck right now with my emotions all out of whack. I can't even really ask my friends because all they know is how negative I felt about her.

Part of me feel like maybe I need more closure, like I should try patching things up with her and at least be friends, but I also feel like that could be a bad idea. I'm stuck.
TL;DR: 
How do I stop feeling like a massive manbaby when it comes to an major ex that I'm definitely not over yet?