I've always struggled with making close friends, but now I want to change it. I've always had plenty of acquaintances and "mates", but one or maybe two close friends at most, as I very rarely feel any sort of deep connection with another person. The only two people I could say I currently truly feel any sort of non superficial bond with, at the moment, are my girlfriend and one of my friends who goes to another university. Most people I just "get along" with.

Why is this and how can I change it?