It is anxiety and paranoia. Try to focus your mind on other things, people will look and move on with their day, you should do the same. Being always occupied by something else whenever you get these feelings will help with them. Try having some more hobbies, put your mind to the test, find something to do out once you start feeling like you're being watched. Constantly do something. Your mind is trying to focus on something, and it decided it's people, maybe your inflated ego has something to do with it.