What should I do ? I can't love anymore...?

Well... My life is very empty. I loved just one girl in my entire life when I was in highschool and she never loved me back, but I really loved her so much. Is now more than 3 years since I finished highschool and now I'm studying at a Master Degree, I'm working, I have a very busy busy life. (even in saturdays and sundays i am going to school for some extra lectures so I have no day off). Even so, my life is empty because I can't love any girl. I don't feel anything for anyone. 2 days ago I asked a girl out, we talked, but I was looking in her eyes and i saw nothing. We just talked... The only girl I ever loved is the girl I can't be with and I'll never can. And every day since the first day I falled in love with her I was thinking about her. 7 years, every day I see her in my mind, in my dreams, even if it is for such a little while (2-3 minutes maybe).

I don't know what to do... Even when I have free time I'm thinking I'm unhappy and sad because I don't love and nobody loves me. And Christmas is coming and I'll be alone. I hate hollidays because I feel I'm so alone and life sucks.

What should I do to fill this emptiness ? Please help...