Assaulted by ex bf roommate..

I want to keep this short because there are way too many details that will end up being lengthy. Long story short, my ex boyfriends “best friend” we used to live with sexually assaulted me one morning after drinking all together at his house (with his girlfriend might I add).

I woke up to him fingering me and tried to pretend I was still asleep but he then asked me if I “enjoyed that” and I don’t even remember what I said but I was basically pretending nothing happened. Mind you I was sleeping next to my ex when he did it.

I never told my ex but made it clear I wasn’t comfortable around the guy and we actually stopped hanging out with that couple for a few months.

Around my ex’s birthday, him and some mutual friends convinced me that I should give the guy another chance and forgive him for whatever I was really bothered about and I did bc I have a habit of letting people walk all over me unfortunately.. but anyways, me and my ex broke up about a month or so ago and he still doesn’t know.

I didn’t think I would ever tell him, but he still hangs out with the guy that assaulted me and I hate that, I feel guilty for not telling him.

Basically I want to know if I should reach out and tell him what happened or if I should just work through it myself. I don’t want to cause more problems than it’s worth but I feel really awful. Let me know what y’all think.