I'm scared of relationships?

I've never had an intimate or romantic relationship. The idea of one makes me feel sick to my stomach... I just can't get over the fact that if I devoted so much of my self to someone, what would I do if they can't accept me for who I am. I don't even know if I'm capable of loving anyone. I never had any form of strong relationship with any of my family, I never loved them, they where aquaintences to me at best. I had few 'friends' to whom I never really viewed as friends; more just people who I spent time with and didn't judge me too much. I knew they would never accept who I really was, so for years I pretended to be someone I was not and the 'friendship' ended merely when I gave up on this disguise and they abandon me after I had abandon 'myself'. I just feel so alienated from humanity. I just don 't know how to express my feelings and it scares me... What can I do?