Are you attracted to your boyfriend's fraternity brother in waking life? If not, I think he might represent a quality in yourself that you are unsure about developing (you kiss him then push him away, then kiss him then push him away). The fact that he is angered at the end is a sign that you won't be able to repress this part of you easily.

The beast vs. heroine scene makes me think of your refined, civilized side vs. your raw, instinctive, animal side.