A few months ago, my boyfriend went to a party. He got very drunk and the next day, after an argument, he told me that a girl at the party had hit on him, saying she heard that he spends hours in bed with his girlfriend (me) and she wouldn't mind having a go, then broke into into the bathroom while he was in there (he said at the time to look at his penis)... the next day, I saw that he had added this girl on facebook.
About a month later, still feeling bothered by the whole thing, I told him I'd seen that he added her and asked him why. He said that she had been insulting his sister and he needed to talk to her. I didn't believe this as a) why wouldn't he tell me about this at the time that it happened? and b) as a friend of his sister, she would have had this girl's number anyway, but I tried to let it go.
It is now a few months later and, after my boyfriend lied to me about something quite big, I got upset again about the whole thing (I just thought, if he lied to me about that, what else could he lie about) and asked my boyfriend again about it. He admitted he had lied about the insult thing and had just wanted to add her 'because he adds everyone'. I know this isn't true, as he rarely personally searches for and adds people, and he ignores requests from ex girlfriends and people he doesn't know.
I'm feeling upset and confused by the whole thing, but he just tells me I need to move on and forget it, since it's been a few months. I know I might be being irrational, but my instinct says something is wrong. I don't want to be a crazy jealous girlfriend, but I personally wouldn't seek any further contact with someone who hit on me, knowing I had a boyfriend, then followed me into a bathroom (which I think could actually be sexual abuse)...
Where to go from here? I hate feeling jealous and mistrustful!
By the way, I'll just mention she's tall, blonde and skinny (physically very similar to me, definitely his 'type')