How would make a boyfriend (specifically) want to break up with you?

If he turns you off, which it sounds like he does. It's you that should break up with him. He told you he loved you after a very short time and he's also boring to you. It seems he isn't what you originally thought he was and that happens to all of us. Don't allow this to keep going on and on so that it gets out of hand. Just let him know it's not going to work out and that you would like to remain as friends. I wouldn't even bring up the word love as it can be misconstrued in a very negative way.