Tl;Dr I been having a hard time since this happened it's my first relationship and cheating, I wanted to marry this girl and now I'm in a scarcity mindset because she had everything I wanted on a woman.

I've been struggling with OCD this last year and my 4 year relationship was paying the price. My (ex-)girlfriend suggested that we'd go on a break and I would take the opportunity to have a treesome as she was too Catholic to be in one. I didn't want this but she pressured me into it. The break would last for 3 months but that is besides the point. I moved to my dad's place to recover while she stayed at our place. I tried to go on dates but my game was shit, I wasn't confident and my OCD probably didn't help either.

This monday I go to invite her to come have dinner and I hear another guy at our house. I confronted her and learnt that she had sex with him.

I'm fucking devastated. I want to be stoic but this hurts fucking too much. I'm trying to be with my friends and family.

I have several questions:

1) how do I get rid of the scarcity mindset? I know I have to spin plates but I eventually want to have a partner and kids I wanted a partner like her. I don't know where even to look.

2) how can I ease the pain?

3) how can I stop carrying about her?

4) how to proceed?

5) who should I share this event with?