I have always had these types of irrational fears too. Especially whan people around me laugh, or when I walk into a group of peeps I feel like they change the subject because they were talking about me. This will sound rediculous, but every once in awhile when I'm sitting at my desk at work or walking through the grocery store, I will for a split second or two think I'm naked and this gives me a fleeting panic attack.
Like sugar said - you are not alone.