Hey Joanna,
Please do yourself a favor and go to a support group. I can't tell you how nice it is to see and interact with others in the same boat. One of my best friends is a mtf transwoman and it has been a huge relief to have her as a friend and a supporter. I didn't meet her at a support group, but having her as a friend has made me feel much more comfortable with myself. Personally, I used to be terrified of going to a group and still get shy about it. Like you I am very shy and avoid group gatherings. However, everyone has been so open and accepting to me so far. Plus, I have been going with friends in order to break me out of my shell. At the meetings, you get people from all different walks of life. I have been in a group with teenagers and people that are much older. It really is interesting to share similar experiences with a group of diverse people. The only down side for me has been that I don't know many girls in my own age group other than my friend. It seems like people are either younger or older than me. I agree that it is easier to have girlfriends who are closer to your own age.
I would go to one specifically for trans people. Honestly, these groups are open and accepting. No one is there to judge or out you. It's a place to open up and be yourself. Please go to one! You will have fun! It's like a miniature version of susan's in real life. Also, you should really take advantage of the Philly Conference. It sounds like a great place to meet new friends. I'm jealous that they couldn't have done it here in NY, so count yourself lucky.
P.S. If you ever find yourself in NY, you know one transwoman that would love to go shopping