How do I break up with my boyfriend?

I am in a relationship I hate. The boy I am with is 3 years older then me and he is so clingy and so in love with me. We are in a long distance relationship and see each other about every month and a half. It is perfect when we’re together but when we’re apart all we do is fight. I don’t even look forward to talking to him and all I want to do is break up but I can’t. He is so in love with me I will break him. I feel like I’m all he has and if I end thing i will mess up his whole life. I put in a hint that I wanted things to end and he had an anxiety attack. He said he cant lose me and I’m the only important thing in his life. I still want to be friends but I feel so stuck in my relationship and unhappy. I don’t wanna make him unhappy tho. So should I just stay in the relationship and be miserable and at least he is happy or how do I break up with him.