Struggling to Control My Emotions in My Relationship

I feel like I'm going crazy. My boyfriend is my favorite person in the world, and honestly the only reason I'm still here. And yet all I do is make him feel awful, I go into episodes and just shout at him and complain about all his bad traits. It feels like I can't control my mouth. He doesn't want to break up with me though, but I really feel like that would be best for both of us. He wouldn't have to deal with someone that clings onto him only to get pissy at him and then beg him not to leave afterwards. And I wouldn't feel like a bad boyfriend after yelling at him because, well I wouldn't be able to yell at him. But at the same time I can't live without him. I know he understands, but it just feels like I'm unwillingly ruining our relationship and it's all my fault. I can't control myself and it terrifies me