I have girl issues/commitment issues?

See, Im really loud, happy and outgoing (I belive in Freiheit and Love for everything and everyone) And I do not hate at all (although I can be mean or a "hard ***") And I love being in a relationship sex or no sex. But within 2 or 3 weeks in I feel like I need to get away from them, like I feel if I stay with them I am going to hurt them (note:I have "gentle" issues I cant be gentle twoards any one without hurting them or inflicting some kind of damage and I hate it:<) So i usually break up with a girl within a couple weeks. And if a girl asks me out or likes me some times I say no without even thinking I will just tell them no. I could really use some advice please?