Scared to be in a relationship again

You can say that I have been traumatized. How can I get over this fear? I want to be in a relationship again and I had a lot of opportunities to be with somebody, but I got scared and I always leave them before we can even go far. It's unfair for them to be with me while I'm like this. I don't think I can be in any relationship at all. I always think it will end badly. Worst than my last one for sure. I don't know how to be fix this. Any advice?