Long story short, I (22M) met a girl (22F) and we hit it off. After a month of seeing each other, I found out her ex visited and stayed with her for three days. She was honest about it, admitting she was conflicted and they hooked up.
I'm hurt because she didn't tell me when her ex came over and lied about being busy during those days. We weren't in a committed relationship but had agreed not to see other people.
I'm unsure if I can trust her again. We tried to remain friends, but the attraction between us made it difficult. I told her that if she wants us to be together, she needs to cut her ex out of her life completely. She agreed.
However, I can't stop overthinking about whether she's still in contact with her ex when she doesn't respond to me. I was never insecure before, but this situation has me constantly worried. She was with her ex for five years and claims she has no feelings for him.
I really like her, but I don't know if I can fully trust her again, but her treatment of me has only improved since this incident.