I broke up with him, but it's still not over

I broke up with my boyfriend because I wasn't happy in the relationship. Besides, It has always been a long distance relationship. We even met online and he is from a different city. He thinks and feels that, that reason isn't a valid reason to call for a break up. He tells me he can try to make me happy. But that's the thing, I dont want him to "try", it has to come naturally. I dont feel like I want to stay in the relationship at all, but the thing is he's really sweet and he hasnt done any of the genaral bad things that would lead me to break up with him. We've been together for more than a year, so I am attached to him as well. If i quit talking to him, he loses his shit and starts to spam me. I do not know what to do... I have already told him that we cannot be together and he just does not want to accept it. Even I need to stay away to be away from him and to be ok without him in my life, but he doesnt want to stop all communication with me. Please tell me if i am doing the right thing? Is not being happy in the relationship a valid reason to break up? or am i over thinking this?

Your BF doesn't need to do any of the 'general bad things' for you to break up with him, rather all you need to do is consider your happiness, which you have done. It doesn't matter if it's been LD or that you met online, what does matter is what the relationship does for you and if it's not doing it for you, then you're doing the right thing by ending it and walking away. While you have tried to explain to him the reasons why you ended it, his actions tell you that you will possibly need to block him completely for you to be able to get on with your life without him.