What seems to be major girl problems?

I can't live my life anymore because of girls. The one girl that I fell in love with I treated horribly and now years after learning my mistakes I tried to make up for it. She told me she was in love with me too but couldn't leaver her boyfriend, which I understand. This type of thing has been our relationship for over 5 years now and the last time we spoke, she walked away and left me alone. She said that we'll never talk again. This really messes me up. I can't seem to get over any girl I ever date, and I always take it so hard. I just can't seem to live my life anymore with out constantly thinking about her. Or the first girl I fell in love with. What the hell should I do. I would love to have a girl who cares about me and actually wants to kiss me and hold my hand. Thats all I want, why can't I get it. But in the same sense I would be okay if my mind didn't torture me so much. Please try to help me, I just don't know what to do anymore.