What do you think my boyfriend is going to do or doing...or what do you think about my pathetic situation?

Okay, i know this is really long, but please just give it a chance and read it...I feel just a bit odd asking someone or something that i dont know this, but I've been with this guy for a year and 8 months and you see, you have to understand first off that it was absolutely perfect for the first year...and once it got maybe a week past the one year mark things started going down hill, such as i found out that he was still doing drugs after i had asked him not to do any anymore and he promised and swore and everything else to my face that he wasnt going to (yes i know im freaken oblivious)...and then this stupid ***** moved to where we are and i found out that she was majorly flirting with him and crap, but supposedly no cheating happened, and then there was a graduation party that his cousin had and of course, considering the fact that i have parents that will not let me do ANYTHING, i wasnt there, well anyways, i find out that he got really drunk there and crap, and one morning i get this call from my friend that wasnt there but anyways, she tells me that he cheated on me with his X-girlfriend and had sex with her when he was drunk and crap (SUPPOSSEDLY!!) well i ask him about that and he denies it hard core, of course, and i talk to the source that told my friend that called me, who happens to be my boyfriends X-girlfriends sister and she said that her sister had told her herself, saying that it was true that they did have sex at that party and that she did notice them leave once, but then she goes and says she did not witness anything and all the stuff shes saying was told to her by her sister (my boyfriends stupid ***** X)

...you see, that girl, my boyfriends X, is a compulsive lieing *****, and all of the information i was getting was all originated from her, so how can i believe it? how the heck am i supposed to know?! it drove me crazy and it still does to this day (that was several months ago)...yup since there seemed to be no witnesses and everything originated from that stupid whore, im still to this day unsure on wether he cheated or not...and the reason i dont just beleive my boyfriend is because one time he went to church where i was so we could be together, and i noticed that his eyes were really bloodshot, so i questioned him and he denied it straight to my face. FOR 30 FREAKEN MINUTES, he lied straight to my face, with the most sincere eyes and facial expressions, telling me things such as i swear on your life that i didnt do any drugs and so on and so on....i cant believe that crap...well anyways he addmitted it to me after that thrity minutes, literally no joke it was thirty minutes of me knowing he did drugs and him lieing to my face. yup so thats one reason why i dont believe him anymore...hes done **** like that other times too, which obviously makes it worse. Alright, right now as in as i write this, hes going to a new years party to some persons house he doesnt even know, with some of his family, including his parents, who could care less what the hell he does, no joke. honestly his parents incourage him to do stuff...yup well now im sitting here freaken stressed as hell because theres no telling what the F is going to be going on over there and it drives me flippin insane because i know he'll just lie about it if he does do something, either that or i can interigate him for over an hour untill i finally get something out of him, hes an expert liar. Why do i put up with this? i dont F'ing know. i swear im the most forgiving push over you would ever come across in your life....ive dealt with so much stuff its insane, no one has any idea, ...i really love him though, and there are still a bunch of great moments in our relationship...im trapped....hes like a drug, though honest to god ive never done anything before, i know its bad for me, i can try to break away, but it just seems impossible, even though it hurts me staying with him , i feel trapped...and i love him...but i just thought id ask someones opinion on what you think about the situation and how likely it is you think he will cheat on me or lie about drinking and drug use....i dont know theres so much more i could write to help everyone understand more but im sure nobodys going to read this anyways because of how long it is now...