Have I done something terrible by letting him go?

my boyfriend and I have been going out for 18 months. on our 18th month ann. we got into fights at school about whether or not I can talk to some people. at home we were still fighting but later on we were ok. the next day at school came and I went up to the same people (girls) the only prob. with that is there are guys by their lockers that like me. anyways my b-f got angry and screamed at me in the hall. we were sharing two lockers together and he threw all of my stuff out into the hall way and he went off to class still screaming bad things about me. I was late for class because I had to pick up all of my things. after that I decided just to blow him off and ignore him. so I went back to my friends lockers he came everylocker break and pushed me aside and yelled at me and once he even pushed me into a locker. after school on the way home I was basically telling him we were over and at home I did. he blew up and went crazy. he started taking things in my room and threw them around. I got scared and triend to escape through another dorr that led outside but he grabbed me and threw me on my bed and started yelling at me and even hit me. I started screaming for my brother to come and help. once I got away I screamed for them to get in my car. by then my b-f had gotten a knife and put it to his head he said he would kill himself if I left. I got in my car with my sibs. and he tried to pull me out my bro. got him off me and I drove away. a while back we did his family a favor by letting him stay with us for a while. but now is on his way to FL. for 18 months he made me be all he had and he was all I had. now I am alone. I know I dont want to BE with him but I want him as a friend, am I being stupid. I cant sleep and when I do its only for an hour and then I get up. is this just a stage? I feel like I will be alone forever. nobody will like me like that again. it happened on a friday so when I go back to school without him all of his freinds will gang up on me because they never even got to say goodbye, but then again I didnt either. I had to run away from my own house from him seeing him put a knife to his head thinking I could come home with him in my house dead because of me cause I left the house. I will miss him forever. should I have not let him go. please keep this story to yourself whoever reads it. thanks