Was I assaulted?

I've been with my current bf (A) for 5 years now. When we were in college (UK college so I was 17) we went to a house party. At one point I remember stressing bc I couldn't find A, then his best friend, B, (who I was also close with) told me that he had seen my bf with another girl and had walked in on them 'doing stuff' as he called it. I was a mess, I was so drunk and emotional. Then B started complimenting me and telling me that he's into me and it's a shame that his best friend is my bf. He then went on to say that I should get A back for what he's done. So, stupidly I kissed him. It didn't last long because it felt so wrong for me. B said it was okay that I stopped and so instead we just drank more and talked. The host let us all stay over and I slept next to B, purely because I needed comfort and he was a close friend. By this time I was so drunk that I could barely speak. I remember B feeling me up when everyone had gone to sleep, and he tried touching me there but I crossed my legs so he couldn't. At one point in the night I woke up to him holding my hand and, without knowing I was awake, he put my hand on his penis. Straight away I moved away. I woke up properly in the morning and B was laughing to me, talking about what me and him did during the night but I didn't know what he was talking about bc I had stopped him, I think. I also later found out that nothing happened between my bf and any other girl. I feel so guilty even though I'm not entirely sure what I did. Is this assault?