Did I cheat?

My boyfriend and I have been together for 7 years. We started dating in high school when we were 15. When I was about 17 or 18, my friend and I were hanging out with two of her guy friends. One of the guys liked me but I did not do anything to encourage him or anything like that. But at one point I found out that he told my friend that he “liked my ass” when I left the room, and I still continued to hang out with them. Then at one point he grabbed my bra out of nowhere and tugged it upwards. I felt really uncomfortable and didn’t say anything but kept wanting to leave after that. I didn’t hang out with them again. I told my boyfriend and he is really upset with me for not saying anything. The guy knew I had a boyfriend and this was about 4 years ago. I feel really guilty and don’t know why I didn’t tell him to stop 😢