Please excuse me while I attempt to put a positive spin on an otherwise terrible situation.....

First, you are not a monster. If you were a monster, you wouldn't care about who you are hurting.

If I'm interpreting you correctly, it was just recently brought to your attention that your behavior could have led to the failings of previous relationships? So this is a brand new thought for you? How confident are you that your boyfriend's interpretations are correct? If you feel this is valid and accurate, don't despair. It's doubtful you've been entirely responsible. Even if you were (which again, is doubtful) you didn't know you were doing it. You didn't do it on purpose, or with some manical, premeditated agenda. You lost control, it happens. There is a saying "when you know better, you do better". Now that you recognize the pattern of pushing people away, you can begin to figure out ways of improving things.