Social anxiety is a real burden to live with. I'm in the same boat that you are, even when people are being very friendly with me and are obviously interested in getting to know me I can seem so uncomfortable that it is off-putting to them. I've been accused of being stuck up before when honestly I'm just very shy. If I could suggest anything that is fairly easy to start thinking about, I would suggest garnering a sense of style. Buy clothes that make you feel comfortable and make you look good- even if your look is unconventional the ability to express one's identity through fashion builds confidence.