Dating a Twin? Might have feelings for both?

For the sake of making this easier...lets call one Twin Lucy and the other Mary

I met Lucy a year ago before meeting her other twin....i was very attracted to her and i got along with her very well. We shared a class together. Now i hung out with them but i never really talked to the other twin because she was a lot quieter....but when she did come out of her shell she was a lot like her sister....WELL Lucy made me realize i was gay, i'd never been attracted to a girl before and i developed a crush on her. Both the twins were gay and they were both in relationships...Lucy started dating my other friend, and Mary was in a long distance realtionship. They both got there phones back from being grounded from a LONG time and i made a point to txt Mary more because i didn't know much about her. Then i started developing feeling for her as well. (FUUUUUCK) we admitted out feelings for eachother...and we started dating. I even confessed that i used to like her sister. But i each time i see Lucy my heart skips a beat too. Is this because i still like her? Or because she looks like my girlfriend? Because i met her first? I really do love Mary. But i am still very attracted to her sister. HELP?