I have the SAME problem, KitschKitten. (I also love your avatar!)
I, too, hate attention and it makes me really uncomfortable to be the center of attention. A friend threw me a BEAUTIFUL party when I finished graduate school and I didn't enjoy it at all because it was confusing for me to have so many people around that cared about me and wanted to celebrate with me and dote.
Here are two books that helped me tremendously and made me start in on flirting and making friends without using being fat as an excuse to wait before dating and flirting and making new friends.
Ten Days to Self Esteem by David D. Burns
The Feeling Good Handbook by David D. Burns
Undoing Depression by Richard O'Connor
Granted two are by the same author, but I liked the first so much that I bought the second. It walks you through good exercises for changing your thinking and has interactive exercises so you can practice and use them in real life. It's a written version of what would happen in Cognitive Behavioral Therapy and many therapists use it as a training guide for their sessions.
The last is by a doctor who was suicidal and depressed for most of his life so it brings a nice perspective.
I also know how annoying it is to get advice when you are feeling badly and it took me so long to get to a point where I was willing to even open these kinds of books. It worked for me...but literally after YEARS of having them on my shelf, unread.
If you're ready, get the Ten Days one first since it's shorter and if you enjoy the exercises upgrade to the Feeling Good Handbook.
Much information, but your post really struck me because I can relate completely.