I Think My Relationship Is Over.... Long

:( my problem started a year and a half ago (well I found out about the prob a year and a half ago but I guess it really started 2 years ago.) my bf became friends with one of his buddies female friends. It turned out that my bf felt that we were having problems and he couldnt talk to me. He chose to talk with this girl on the phone almost every night for 5 months. Some conversations were only a few minutes long others were hours on end and sometimes back to back phone calls perhaps when I would call he would hang up then call her back... We live together, have for 3 years now. So these phone calls were all behind my back and im pretty sure all of them were while he was out of the house. I saw this girl at his work one night and my instinct with how they both acted was something was up... I asked, he said no.. I dropped it. But the feeling still lingered. I came home from work one night to see him sitting in his car on the phone. He immediately hung up and said he was talking to so and so (not her)she called back he silenced the ring making some silly excuse. I pleaded with him to tell me the truth he stood by his story. About 2 months went by and I for some reason decided to check his cell bill and found countless phone calls to and from the same number at very odd times of the day/night. I called it... It was her. I went back all the other months and had hard evidence. I confronted him he lied said he let his buddy use his phone and he probably called her.... Yeah... Like I said hard evidence... I cried.. Decided it was over cried and cried. He cried and some how convinced me that it was only phone conversations because he needed to talk to someone about us. It took days for my to get him to admit that he had more feelings than that for her and that he is stupid if she didnt "fall" for him in the process... Hey, im a girl.. I know the easiest way to get the guy is to be attentive to his needs... Say the right thing... Right?? Anyway, he promised that the friend ship and the calls would stop and to my knowledge it did immediately. He has no unaccounted for time since and no odd phone calls. My problem is that I cant seem to get passed it. I dont think about it anymore but I find myself very jealous now and when we do argue it almost always comes up. I hate that it does but I still feel betrayed and cant seem to let it go. I love him very much but it gets worse... In a different way and now I really dont know what to do. Our sex life in the past 2 years has been insanely almost non existant. I used to keep a calander but it got too depressing so I stopped. I try to do fun and sexy things but I get turned down by the "im tired" "i dont feel good" or "im working" stories (he is a busy man holding down a part time job and running his own business.. He also has to study a lot for this business which keeps him busy) but to me sometimes excuses are to often. I have never had a problem with arousing a man and have always had very healthy sex lives with former boyfriends. It has gotten to the point that I really want to leave. I try to talk he clams up (hmmm.....Kinda funny considering why he felt the need to call that girl a few years ago) I finally got him to talk the other night we let it all out in a non argumentitive conversation we took critisism from eachother as well as compliments. It was great. But I told him that I feel the relationship has endured far too much damage and I dont see that it is fixable at this point. He wont seem to let me go!! I know I am in charge of that but it seems that he has the right things to say to keep me from following through with it! Im a mess. I dont know what to do! But I am 98% sure I want to move out and on with my life. I really do love him but the way our sexlife is I cant help but think that if he isnt having sex with me then, who is he having sex with?? C'mon.. No one goes 2 mos or more without sex when they have someone laying beside them every night. Well, except for me that is... Lol I feel so rejected and so alone. He wont even touch me. If he wants to have sex he seems to think i'll just "know" he doesnt try to instigate it and since I have been turned down so many times I dont even try.... Im 31 years old and look much younger. Im very healthy and have confidence in my looks. We have been together now for just over 5 years. Please can any of you offer any advice? Have you been through this or know anyone who has?? Im at my wits end and I cant talk to my friends because we have almost all mutual friends and I dont really want any of them in our business.... Please help