forever lost i guess

I started dating this guy 5 months ago and he was really sweet. my friends hated him, they would pretty much call me stupid and desperate for dating him. he was so sweet at first, until he wasn't. he would often tell me what to do, but he would never ask. it was his way or no way all the time. he would get mad over the smallest things in class and would find "loop holes" (as he likes to call them to find fault in whatever i say. he'd ask if i wanna get married, I'd say no because at the time it had only been about 2 months. the answer is still no because we're still in school. he had started to take up some of my time, my friends would get frustrated because they wanted to see me too and i couldn't reason with anyone without loosing the other. In short i lost all three of my closest friends and i have a boyfriend that makes me feel like i have to stay with him or else loosing my friends would have all been for nothing. he has all my account passwords except for this one, so i cant talk to anyone as he frequents the accounts daily. he calls me a sl*t because I've had 2 boyfriends before him. he had five. not that I minded. its just that is is too much for me, i dont know what to do, I want to go into the Navy but he threatened to unalive himself if i did. I'm so frustrated and isolated, i feel like hes the only one that understands me but hes also the only one that hurts me. I dont know what to do. this post is so all over the place I'm sorry