I'm scared to let people get close to me, even my boyfriend

My boyfriend and I have known each other for several years.

In all that time, he has always been kind and considerate and has never done or said anything that would hurt me. This is the first serious relationship either of us has had and we have a lot in common and enjoy spending time together.

But I'm scared to get emotionally close to him or to trust him. I've never found it easy to trust anyone, but I'd thought I could find it in me to trust him after all this time.

Now I'm worried I'm going to hurt his feelings because of my tendency to chase people away when they start getting close to me.

what's wrong with me? why can't I trust him? and what should I do?