I'm the same. My friend asked me to go to a Hopsin concert with him a few months ago, and yesterday was the day of the concert but at the last minute I declined because I was so paranoid.
I try to meditate to myself and say words of encouragement when I'm on the bus. That's probably the only thing you can do. That and just push yourself until you have your confidence back.
I'm just gonna start hanging out more with my friends regardless of the paranoia. It's the only way. Especially considering this isn't a physical problem anymore. It's all mental.