Am I going to end up getting hurt by him :/?

(I'm 16 and he's 17) I've liked this boy for about six months, ive never like someone so much and can't imagine myself not liking him. But he's put me through so much crap, basically he liked me and another girl at the same time and might as well be going out with her except he always comes back to me. He'll stop talking to me for a while and then when he sees other boys giving me attention he starts talking to me again. I've tried getting over him but I just can't and now I don't even want to. I like him so much that whenever he comes back to me I can't say no. He told me that the other girl is going away ALL of summer and we've made loads of plans. Will he leave me when she comes back? Will he hurt me again? I'm scared but I like him too much to say no.