He cheated- what am I meant to do?

I've been seeing this guy for a while now- talking every day- not even in an obsessed way, our humour just matched and he was so caring and I genuinely enjoyed talking to him. It took me a while to open up to him and I wanted to take it fairly slowly, not have sex until I knew him well etc. As last time I did otherwise I felt attached too quickly.

Earlier this week he went a bit quiet and I had a bad gut feeling. I knew something wasn't right, but my friends said just to leave him to text me first, so I did for about a week, and he did, but it seemed slightly off.

Yesterday he told me he 'cheated' on me, and slept with another girl he had only known for 1 day- while he was sober- earlier this week, hence the reason he went quiet. I decided to see him in person to discuss it and saw a completely different side of him. He was casually self obsessed, kept changing topic and didn't seem genuinely resentful.

I'm pretty hurt. I also have to see him at work. I'm not sure how to process this all and how I should feel.

I'm torn because to a degree we weren't exclusive - altho we were serious enough for him to feel guilty and the need to let me know, but now I just see he wasn't who I thought he was, and we haven't spoken since I saw him yesterday. It's as if he's just binned me off. I feel like a complete mug.

Does anyone else who has been thru this kind of situation have any advice? Can anyone give me some insight? I'd be so grateful! Just can't help feel a knock on my self esteem, like I did something wrong 🙄

Thank you all!