Why do people suck?

So I am a 19 (almost 20)-year-old man, and about 8 months ago I found out that my girlfriend is cheating on me with another guy. My girlfriend (or ex) had claimed to be very busy with her campus organization, and ever since I found out, she was disrespectful towards me, rarely responding to my messages. Her friend messaged me, saying that my girlfriend is cheating on me with another guy, and they even sent me a photo of my girlfriend with the other guy together.

My heart was shattered. I tried my best at everything for her as we've been in a relationship for 18 months (last 3 of them were a LDR).

I loved her so much, but damn, I was so disappointed and angry. I didn't know if I ever want to find another relationship again after seeing this stuff happen all the time. I had to deal with infidelity growing up and I was always nervous to be in a relationship for that same reason and then bam, back to square one.

Recently, I was trying to get back out to social events which was even a stretch for me as I'm very introverted and don't like social situations very much...and I talked to some girls, and some even came over to me to talk, and gave me some compliments. But every time I would feel a connection with one, my brain would instantly remember how my last relationship ended, and what's to stop this next one from ending the same way. I have a photographic memory so I can't just erase what happened before in several years as I remember it like it was yesterday. Anyone mind giving me advice on how to move on with this? I might just be better off single or maybe trying to find someone online/LDR.