Not sure how to do this

Maybe someone out there has some advice for me. I have been with my guy for 3 years. Things in the beginning were great. Until 5 months into the relationship I was told that his ex (which is still his "friend" to this day) was pregnant by him. He says it wasn't cheating because he wasn't officially my boyfriend yet. But he had just said I love you a couple of months earlier and we were having "relations". I was supportive of him and told him that I would still be there for him anyways. Well, she didn't have his child, she lost it. He continued to stay friends with her and I tried to understand. Then 5 months had passed again and he spent the night at her apt. I found out because I went there at 4 in the morning and saw her car that he borrowed. (It was just that gut instinct besides the fact that he didn't return my calls and I couldn't sleep.) I tried to leave him then, but he wouldn't let me and convinced me of a second chance. Well now that time has gone by she is still friends with him and she is friends with his sister. She has gone out of her way to buy him expensive things that normally he wouldn't buy for himself such as: 36 inch tv, ps2, digital camera, stereo eqipment, gifts from her travels the list could go on forever. She has also gone out of her way to assist family members by throwing parties and catering and hosting them because they are in school. She is included in every aspect of his family's life and I have not yet been invited or been present at one of his family events yet. This boy says he wants to marry me and have a future with me. I don't think I can have that when his ex-girlfriend still lingers on and refuses to meet me and attend our "wedding". (By the way she also punched him in his face because she found out we were having "relations" after 3 years of being a couple) Is it unfair of me to ask of him to ditch her before he even thinks about getting hitched? My dilemma is that I do not want this crazy (she's BiPolar) girl ruining my family with this boy, he doesn't see that. By the way he is going away on a vacation with his family and she's going because "she's invited by my sister" he says. Is my boy double dipping? Angry after all these years.......