My boyfriend is cheating on me and i dont know what to do

I have been with my boyfriend for 6 years and we have lived together for 3 1/2 years. I love him a lot i started dating him when i was 15 and am now 21 and we are still together. Our love is strong and i know this but over the years it has faded. He use ta tell me he loved me everyday numerous times a day now he never tells me. He calls me names, hits me, leaves bruises on my arms to the point where people notice at work and ask what is going on. It's embarassing and when i think about him "loving" me i just wonder why he would do this to me. Not only does he mentally, verbally, physically abuse me but i also found out about a month ago that he has been cheating on me or talking ta this ugly girl. He use to leave his phone around me and have me answer it when someone would call and then a couple of months ago that stopped. He started acting really weird always asking me if i was cheating on him, who i was talking to or messing around with, who i was texting, accusing me of cheating on him everyday even if i were at work i was cheating on him. He started going through my phone checking my myspace but i wasnt hiding anything at the time. He also would give me his passcode to get onto his phone records online, but then when i asked for the password again he refused to give it to me. We were sleeping and i heard his phone go off so i looked at it and it was a text from her saying "good morning baby" i asked him about it and he said he doesnt know the # or anything. So i figure out his password to his phone records since he wont give it to me and go online and he has been talking ta her since june texting back and forth, calling each other. I can't believe it how could he always accuse me when he was the guilty one......but thats exactly why he was accusing me....so he didnt feel as guilty! I asked him about him talking and texting that girl and he said he doesnt know what im talking about, i told him that i looked at his phone records and he got mad at me for going through his stuff....but still lied about texting and talking to her...right in my face and i had the phone records to prove it.....crazy huh?! GUYS ARE IDIOTS~! So i text her and ask her whats going on and why there talking still since i've found out, she said well he called me once and ive called him twice...so i asked him why he called her and he lied again saying he didnt call her and she didnt call him even though she told me that they both called.....i dont get why he's still lying and denying it....i dont get it i thought our love was stronger than this and we "our relationship" was stronger than this...but i guess not!!! Since i've found out they've been talking i gave him the choice to quit talkin ta her or leave and that i cant continue to deal with this or be treated like this...he promises everyday and swears he's not talking ta her but every single day i see her # on his phone records and over and over again he lies about it.....I love him so much and i dont want to throw 6 years down the drain its a lot of time and energy ive put into the relationship!!! but i can't keep dealing with him and his shit! I'm way better than her, she is a downgrade i mean why would he wanna do this?! and how could he keep talking ta her when he knows how much it hurts me, he has me in tears everyday, im upset feeling sick and he keeps talking to her like i dont matter, my feelings dont matter, and im just gonna stick around but I cant and im not. The main reason its so hard to leave is how long we've been together and that i have neva lived by myself before and i hate being alone. I dont like going to the store alone so if we were to break up i dunno what i would do...thats my problem i dont wanna live alone and be alone and sleep alone and just be lonely....i dont get what i've done to deserve this i really dont!!!! I think he takes me for granit and i want him to know what its like to be without me, i just can't make him leave! It's hard to kick someone out who you love and are in love with, have been with for 6 yrs, and to know their going to someone else.....i dunno what to do! I am beginning to hate my life. I feel like i have no one to turn to...I wish i was a stronger person to make him leave and do whats best for me but its hard when your heart and feelings are involved. I also found out when lookin at his phone records that him and my "friend" were talkin and textin each otha a lot....which i put an end to, he lied about it, she admitted it because shes scared of me and apologized but i just cant be friends with someone like that and for the fact that she didnt tell me about it when it first started going on she let it go on for a month....and i was only really friends with her for 3 months, so with the trust being gone i decided to quit being friends wit her,..... He's a dog and i know this but i love him and have loved him for 6 years...this girl hes still talkin ta will neva have what i have and i dont see why he's riskin losin me and our relationship for her!! What does she have that he cant stop talkin ta her! i dont get it i really dont. He went through my phone again though and found this guys # in my phone who yea i did end up cheatin on him wit...but i've neva had an ongoing relationship wit someone else before. Yes i've cheated but neva another relationship its a completely different story. I mean if he gave me the option to quit talkin ta the otha guy and be wit him or keep talkin ta tha otha guy and lose him....i would obviously choose him and to stop talkin ta tha otha guy...i wouldnt want to lose him and throw away 6 years. Im hurt and i dunno what to do i really dont....this is starting to take all my time and energy it also got me started in a life that i neva thought or wanted to live which is addicted to cocaine....i do it everyday, it almost numbs tha pain, puts me in a betta mode and helps me cope with my problems...takes me to anotha place so i dont have to deal wit it...It's become such an addiction that i do it at work everyday, when i get home i have to hide it from my boyfriend but will sneak into the other room and do a couple lines. The sad part about the whole cocaine thing is i steal it from him, he makes me so mad and treats me so bad i dont care i take it from him. I just dont understand what has come of our relationship?!! I wish my life was a bad dream that i could wake up from but its not and if i cant figure out what to do wit my situation one of them is seriously gonna get hurt....i have a bad temper and get angry very easily.....i dont wanna end up going to jail i need out but i dont wanna get out.....cuz i dont wanna leave him and lose him to another girl....it's like im stuck between a wall and a rock and i can't move b/c i dunno what to do....I am leading a life of self destruction....slowly but surely my life is going down hill!!! I dont get what i did to deserve all this hurt and pain. A co-worker of mine told me that he thinks based off what ive told him from both sides that our relationship is over just neither one of use wants to admit it or actually deal with ending it and being alone...we've gotten comfortable with one and another and dont want to leave but both know its over...i feel this is true in someways because there is no trust between us we're always questioning one and another and are always arguing but on the other hand we have our good times and i can tell he does have love for me (the question is....is he in love with me??) but is that love enough to stand through tha lies, desite, anger, pain, stealin, cheatin, betrayel.....thats what i cant decide......I'm torn and wish i could make up my mind!! i want someone to talk to who understands what im going through and has some good advice or stories to share....plz help me.....