How do you overcome a fear of intimity?

Hello, I'm in age where I should date and get married but I think that I'm happy just hanging out with friend without boyfriend. However, I know I would like to date, but I know that I have always been like this and if I don't change myself, I will forever stay alone. I know having a boyfriend would be great, but I'm afraid it will end badly and that it's a closeness I'm not ready for. Btw: recently, I found out my long-term best friend doesn't care about me at all and had to cut her out of my life, because I was expecting her to be there for me in my hard times and she just didn't care to do that so I think that experience also doesn't help. Anyone who currently have/had the same experience? How did you overcome it?