What's wrong with me?

To make a long story short, I am a 42 year old virgin that has attempted time and time again to have a girlfriend. I would eventually like to marry. Everytime I start to "date" someone, it always end in failure for me. It took me a lifetime to figure things out. When I was growing up, I was very different and conditioned to believe that I was "nothing." This continued into my adult life whereby I always feel inept and generally inferior to everyone else. My low self esteem always got the best of me. Through my childhool all the way to high school, I was always made to feel like **** all the time. In college, this continued but only subtly toward me. The first girl I dated ended up making a fool of me. What she did too me made "careful" about others I would date. I never felt confortable and would always feel second rate. After college, I occasionally date someone every few years which would always end up the same way. About a year and a half ago, I started going out with this woman. Again, I could never bring myself into telling her how I feel. There are times that I feel that even our platonic friendship is endangered. I am on the verge of letting her go to find someone else. Tell me something. What's wrong with me?