Hey Elana... so incredibly glad you are back!
I have a particularly hard time with friendships as well... in fact, I don't have one close friend from college. When people start talking about their "college buddies", to this day it makes me uncomfortable.
After that, though... I thought, "Well, I'm not insanely unhappy being a 'loner', but let's see what this 'friend' thing is all about." Despite a staunch resistance in the past to living with people, I basically "forced" myself to live with two girls my age when I went to grad school (who are two of my absolute best friends now, by the way).
I think that for me, it was a decision - I'm not "good" at this naturally, or so I thought... so at first, I really had to make an effort to create and maintain friendships. This even actually entailed accepting invitations when I didn't want to at all... going places where I pretty much knew I might be uncomfortable because of the social interaction... "forcing" myself to call and just chat with friends, even though I didn't want to...
As a result, I really believe I have retrained myself. When I moved, it was almost instantaneous that I found nice people to acquaint with... and then three girls that turned into very good friends. But I had to get comfortable with myself and realize what I was doing (i.e., pushing people away so they wouldn't really know me and then God-forbid not like me)...
It took a lot of time. But I am so glad that I "forced" myself to try... because it is so worth it. Now, when something good happens, I have at least 4 people who are NOT related to me to call and tell. That's just a wonderful feeling. But it really takes time.