It seems to me you are very quick to go into a relationship, and don't really take the time to get to know and evaluate the other party. It's kind of let's try and see how it works.

Looks like for you it does not work. So I suggest you take more of your time to get to know the guys you are interested in, and only make a move after you have cleared some obvious red flags (alcoholic, mysoginist, etc).

Although this seems tedious, I think you end up wasting less time than by continously starting abortive relationships.