Relationship

I feel like a total fool for posting this but here goes nothing. I'm 17 and have been dating my boyfriend for a little over 2 years and we've known each other since 6th grade. We've never been on and off (taken breaks) but we have had lots of ups and downs, which of course is normal. Where it's not normal is that the first year of our relationship he was very verbally and emotionally abusive and had slapped me for not telling him something (I didn't tell him I had gotten with a guy we knew from school.) I honestly should've broken up with him the first time he touched me but I was dumb enough not to. Mind you, I had liked him since I was 10 so when he finally admitted to having feelings for me almost 5 years later and asked me to be his girl friend, I was determined to make the relationship work. Since then there was a long period of time in which we were VERY healthy relationship wise and were super attached to each other and hardly ever had arguements and we were always happy together and coming to compromises when there was a problem. Fast forwarding to the present, we're back on the path towards a destructive relationship. We BOTH have been hitting each other (not punching or hard enough to leave bruising — not that this makes it any better) and he keeps starting irrelevant, useless arguments and he's letting his anger issues and bipolarness get the best of him. We'll argue for the dumbest reasons and both me too hard headed to come to an understanding. I've been more emotional and intolerant to his BS than ever. We have happy/good days, but 60% of the time something negative is happening. Every time I mention how he's going to lose me he eventually tells me his genuine feelings, which I know are sincere, which all together mean that he loves me. I love him too but I'm reaching a point that I don't even understand. We used to have sex 5-7 times a day and now I avoid even having sex once a day which is making him extremely sexually frustrated but I simply don't find the urge. Not to mention I'm super insecure so I feel like when we do have sex he's thinking about other girls and I hate when he masturbates to porn almost EVERY DAY. At times he thinks I'm not attracted to him but that is not the case. Maybe all my classes are stressing me out to the point where my hormones are messed up, but I feel this wouldn't be the only reason. I don't know girls, I guess I just needed to vent. Comment if you'd like. :) :/