My fiance cheated on me 4 months before our wedding

I'm pretty much just using this account to vnt. I feel like this is the only semi-normal sub on this site and there's a lot I just don't want to spill to people I know.

My (ex) fiance and I had been dating for 5 years. We started at 20 and 18, now I'm 25 and she's 23. She was my first and to date only serious partner. I thought we'd be spending our life together. I never saw any of the signs. From my view we were getting closer. And then 2 weeks ago my friend spots her smooching another dude at a restaurant.

I'm full of so much right now. Anger and betrayal of course, but also confusion. Like did I do something to deserve this? I feel like I was always there and tried to be the best boyfriend I could be. We had no communication issues and always had foresight into our future. So what went wrong? Also it's the feeling of wasting half a decade on her. My early-mid 20s, my yung years, were all wasted on her. I could've dated all the other cute chicks who showed interest in me but I stayed loyal. Who knows if this was even the first guy she's been seeing during this time. Probably not.

I won't lie I've basically self-imploded over the past 14 days. I only go to work and come back. I've stopped going to the gym, gained 7 lbs already, and haven't seen my friends or family in a while. I just lie around reminiscing, crying, and watching the NBA playoffs. I just don't know where to go from here. Or how to move on. Like how the fuck do you even meet girls at 25 if you don't drink? Am I seriously restricted to apps? I don't even know if I can trust anyone.