Emotionally traumatised by sex.?

I just need some help/ advice from someone with insight. I just dont know what to do.

Basically its as I said in my title. I haven't slept with anyone, but my first gf, I walked into her having sex with a random guy which shocked me and they were both quite horrible to me and nasty. They even said, I just wasnt good enough ...

It also happened with a second person.

Since then I feel real insecure and traumatised to the point where I dont know if I can have a relationship with anyone. I just wanted to feel special and not like if I met someone, I'm just another guy and not the one she wanted all this while.

I dont know if this makes sense, its just hard for me to talk about but I thought I would ask people here for what to do. I just wish all this never happened. I wish I could be normal.