Girlfriend's ex is obsessed

im going out with this girl who broke up with this guy awhile back but he is obsessed with her. and he even puts his arm around her when he thinks im not there, so I've seen it and my girlfriend has told me about it. heis trying to steal her from me, but she is hates the kid. he is getting annoying fr me and my girlfriend. what do I do?

tell him to back off.. or tell her to talk to him.. he has no business butting into your relationship.

If she hates him then why does she go around him?
If you saw his arm around her then she obviously doesn't mind it being there or else she would moved away from him or take his arm off of her. Seriously though think of it... it takes less then a second to take someones arm off you or move away from them, so how could you possibly see his arm around her with her actually not wanting it there?

okay let me put it this way I've seen him try to do it