I NEED RELATIONSHIP HELP!?

I would say I’m horrible at relationships but somehow I always end up with a boyfriend, don’t ask me why I’m not very attractive but somehow I get them… anyways after about a month I repeat the same cycle of dumping them without a reason and they are left annoyed and hurt.. but now I find myself in a relationship with my best friend and I truly love him, as a friend, and never want to lose that and I don’t know what to do because in my heart I know that we would be great together in the future and I could potentially fall for him as a boy friend but I’m psychotic in relationships and could ruin this before it has a chance… ANY SUGGESTIONS???? How should I act and stop all this? We’re in a fight right now because “I don’t show enough emotion” but I’m not one for pda and he said I’m acting like if he broke up with me I wouldn’t care and I don’t know what to say to that? I don’t express my feelings vocally.