Relationship/Breakup/Infidelity advice?

This is going to be a little long, I'll try to keep it as short as possible.

I've been dating my boyfriend for nearly 3 years now, and we've lived together for over 2 and a half years. Needless to say, we moved kinda quick. When we started dating I was fresh out of a nearly 2 year relationship, and I told him I didn't want anything serious. Obviously things changed, but whatever. We have a lot in common, we get along pretty well for the most part, and he treats me pretty well.

Around a year and a half into the relationship we stopped having sex as often (cut down to maybe once a month) and we used to fight about that and a lot of other things all the time. Its gotten a little better in the past 6 months to a year, but not by much. We dint fight as much anymore, but I've become pretty unhappy and dint see us together for the long run for awhile now.

We moved in with one of his friends about a year ago, and we dint have as much money problems as we used to (therefore not as many fights). But our roommate has this friend that's over here alto; we'll call him Bob. Me and bob connected pretty much immediately, and have just as much (if not more) in common as me and my boyfriend. In order to cut this short, I'll just come out with it and not beat around the bush with too many feelings or emotions... I've basically been cheating (on and off) on my boyfriend with bob since November. We've taken a few breaks here and there, but they never lasted.

My boyfriend is clueless to all of this, and by now considers bob a pretty good friend. The thing that makes me sound like an even worse person is that I never really felt all that bad about it. I knew it was wrong, and when me and my boyfriend would fight I'd even be glad I had bob on the side. But I never felt/feel bad enough to end it for good. I think it's because I know me and my boyfriend wont last.

So the problem here though is that my boyfriend is still very much in love with me. He tells me all the time how he'd die without me and how he wants to be with me forever. But there are times though when he doesn't make me feel the least bit desirable, and I feel like he's just with me out of comfort. There are also times that I feel like, picked on by him. He'll randomly come up and just bite me, or start play punching me, and I constantly have bruises because of him (I'm pale and tend to bruise easily, but still). When we fight and I try to walk away he'll try to stop me by manhandling me to the bed or against a wall. I made him promise me awhile ago to not do that to me anymore but he still does on occasion. I catch myself kinda being mean to my bf, I think I might just be trying to get him to leave me. I've tried to break up with him even before Bob (and still a few times during) but my boyfriend never lets me. He never lets me leave to even cool off, when we fight we have to fight it out and end it or nobody leaves.

And then there's bob. I was never really happy with myself or how I looked, and bob seems to be the only one that has tried to change that. He compliments me anytime he can, he tells me what he likes about me (not always my physical appearance), and has been the ONLY guy to compliment how I look when I'm all naked and vulnerable and wanting to cover up. And it just seems like a struggle to get a compliment out of my bf. He'll always tell me he loves me, but rarely tries to build me up unless I ask for it. I'll say this though, both of these guys have some shortcomings...not just my boyfriend.

I just know I dint want to be with my boyfriend anymore, I dint really know how to achieve this though without him losing complete hope. How do I make him understand that we're just not right for each other right now? I'm definitely NOT coming clean about cheating on him, because I never did this to hurt him or anybody (if only myself). I know that sounds stupid and crappy to say, because cheating on somebody is unforgivable. My bf's done so much for me, so I can't help feeling like an ingrate. But its just over for me, I dont know if I can get it back.

Obviously I shouldn't stay with someone out of obligation, but how do I do this? I don't want to have to pack up while he's at work one day and just leave...but I dont know how to break up with him and he never lets me. Plus I dont want him to not be in my life, because he's a good friend through everything. Do I just run away with Bob somewhere far away and move on with my life and not care about what happens to my boyfriend? How do I get him to just let me go without having to hurt him even worse by being honest about what I've done?

I haven't told anybody about this, and I just need some help.

you need to be honest with yourself first.....you have a lot of short comings.....one of which is you dint know what you want.....nor do you speak your mind.....I think you need to be thinking about what you want...and trying to achieve that instead of going for two men who may or may not be wrong for you. good luck : )