Friends with Benefits!??

My friend.. I'll call him Dragon, just the other day asked me if I want to be freinds with benefits!
We both are in long term relationships, we've been at uni together for about 2 and a half years, same as my boyfriend who I only recently became sexually active with. I declined politely but then he sent me some... what I can only describe as.. graphic photos. And I had to tell him to stop 4 times before he stopped sending them!!! We're really good friends and I trust him, but I'm going over to his house to watch the old batman movie with Jim Carrey on Tuesday and I'm a little worried he might try something on. He's done that before but he stopped when I said to. So.. I'm sure he will stop if he does try something. But he kind of made some rape jokes the past couple of days.. involving me in them... But we've always wound each other up like that, I call him gay cause I know that annoys him, and then he'll make rude jokes and suggestions which he knows embarrasses me. I'm probably just over-reacting. He wouldn't hurt me, I mean, we have to study together for another 2 and a half years!
Yeah, I haven't told my boyfriend all this because I'm worried that it will cause so many problems for lots of different people and it would be all my fault. I don't want a repeat of when I was 12... I just really needed to tell an uninterested audience my feelings and worries before I did something stupid again.
On a lighter note, (´ ??).??? ~~~~ I LOVE Monkey!!!!! ^^
ps, I've decided to call my boyfriend Monkey on here cause he love Monkey D. Luffy and he's actually alot like him! ?????