Is she after my man?

Ok.... my boyfriend and I have been together a little over a year now and there is this one friend I and many others cant stand that he hangs out with. They have had sex with each other and I think something is up. Like every weekend he goes over there and does soemthing with her (like go to town or something). during the week they talk on the phone more than what me and him do. I think something is up she goes to eat with him, rides around with him and everything and it is buggin me. me and her was talking the other day and I told her how I felt about my boyfriend going over there and she just said "well obvisously he dont care what you think about it" that made me soooo mad. I have to call her sometimes just to see where my boyfriend is because he aint ever at home and he dont answer his cell when I call. She says well he is my best friend and he says baby we are just friends nothing is going on. tell me please if this isnt true.. after you and a friend f**k you cant be just friends something has to be there. I think she likes him if feeling are there. I dont think he really likes her but I could be wrong. I mean I talk to her and I ask her if she has any feelings for him and of course she isnt going to tell me but she always says no!! we broke up for a month and when we got back together he told me that he wouldnt go over there to see her just to see her dad (b/c her dad and him are close) and I dont really like them even talking to her. And he knows how I feel about this but the only thing he says is baby nothin is going on we are just friends and you know that I love you. like if he comes to see me after hes sees her he acts kinda weird around me. what should I do? should I trust him with her? which I aint going to ever trust them together...but Help please!!!!

wow! that is a big problem. maybe when he goes over her house or out to eat with her or anything else they do together you should volunteer to tag along, and if things seem like they are more than friends... well there's your answer.