"I am incapable of caring about anyone other then myself,I do
feel guilty about all of this"
I must disagree. It doesn't seem like you are caring about yourself at all. I would say rather that you are incapable of caring about yourself. Did your so called selfish act make you feel better? It did? Yeah, how's that working out for you now?
The thing is, folks that make a rough life for themselves and feel bad inside (as you are now) seem to be under the impression that folks who are kind are unselfish. It's quite ironic; you think you are being selfish but you're truly making yourself miserable inside when you thought you were doing something for yourself. As the Dalai Lama says, altruism is the ultimate form of selfishness. Folks who behave in this way have learned how to get joy by the fact that interactions with us makes others feel good. We begin to care about ourselves and feel good about who we are. Sometimes I count myself with this group, sometimes not, but I work on increasing my time spent feeling good about myself, gauged on how I affect those around me. I care about people, and I reap the benefits. In the areas of my life where I am most successful in giving and connecting, those are the areas where I get the most incredible love back, my marriage, my family, my relationships with friends and coworkers. The love I receive from these areas is incredible and it fills my heart with joy.
So you don't know about true selfishness. I encourage you to learn - it is a beautiful thing. :-)
This is all a process. You know my thoughts on the girl; I only hope you let her down gently and the rest is for her to get over. I think there is much for you to gain from this experience.