I can honestly say that I could have written exactly what you wrote. I have the same problem... I hate not having close friends, but I don't LET people get close, so I can't really complain. I have trouble making friends my own age, a lot of times, because I feel like their priorities are not in the right places, and I just don't get along well with people. I have a few 'friends' who I hang out with sometimes, but I would not say I am close to them, we don't talk and open up with each other.
I can't try to give you advice on how to change, but I can tell you that you aren't alone. Maybe the problem is that the people you're meant to find, to be good friends with, are walking around with the same kind of shells on, and no one can understand it.
Anyway, if you ever want to talk feel free to
PM me. Maybe we can figure it out together?
I do want you to remember that there is no reason for people to reject you, and you have to give them a chance to really know you.