I can sympathise with you. I grew up convinced that I was fat. My brothers told me so, and my mom loved to tease me as well... So I thought I was.
This conviction changed me into a shy, introverted person. It affected the way I dressed, the way I looked (or didn't) people in the face, and the way I acted. I found myself a husband who would also tease me about my tummy. I believed it was true. I had kids. I gained weight. A lot of other stuff happened.
And then the most unbelievable thing happened - I started doing things I enjoyed. And I did more of them. And I was able to be enthusiastic about those things. And a good feeling started to grow inside me. And I discovered I actually liked myself. For the first time.
Several years on, now, I can look in the mirror and see a beautiful woman. I can stand still and feel myself to be a beautiful woman. The reason is a selfconfidence built on knowing what I love in life, in people, activities and myself.
I hope this story helps you - don't fret about not having a relationship. Start figuring out what you love in life, and do that stuff. This will light the spark of beauty deep inside you, and you will attract the kind of man you need into your life. Start working on you first. It pays off big time.
A book that really helped me is by Clarissa Pinkola Estes - "Women Who Run With the Wolves: Myths and Stories of the Wild Woman Archetype." It started me looking for my bones in the desert. Find yours too, rebuild and transform!