hey silent. no this is definately part of your mental health issues and not real. you are not being followed or watched. do you have a doc who knows about your issues? if so and if this paranoia is interfering so much it might be worth mentioning to her/him to see if s/he can help at all?
good luck and try to trust your logic as much as you can rather than your fear.
oh and i can add that i cant ever recall seeing any post with your screen name on it either if that makes you feel any better.
take care
biiv