I get paranoid about people watching me. It's why I wait til like 11pm to put my rubbish in the bin the is like a 1.5 metres (maybe 5 feet?) from my door. It's normally not that bad that I've feel the need for anything, but recently I saw one of my neighbours watching me and the really set it off that night when I had to take the rubbish out - I stood at the door and balled my eyes out. Next day I couldn't handle people and if anyone got too close to me I felt like I was gonna fully freak out. That's why I'm now on Seroquel. Feel better for it.
So yeah, please don't think you're alone with paranoia. Like the others have said, you learn to cope
((((((((HUGS EVERYONE))))))))