Am I paranoid or am I overreacting?

I think it can be normal to feel occasionally nervous about an open window, or something that you tend to anthropomorphise, like a stuffed animal, even if you know it can't actually see you (thats why it can be a common site in movies and tv for a person having sex to turn around or face down a photo of family members). And you're aware that they can't actually watch you, which is a very good sign. But if these feelings of paranoia are constantly stressing you out, or making things like getting dressed or just being yourself while alone difficult, than it might be an unhealthy amount of anxiety, and it may be a good idea to seek out some support or advice from someone who knows a lot about anxiety, like a professional, or someone who has experienced anxiety and paranoia before. Whichever your most comfortable with, or any other solution, if you think of one. You deserve to feel safe from being watched in your own home, and I hope you can find a way to be more at ease.

Earlier I stumbled upon this book:
http://www.amazon.com/Dead-People-Watch-You-Shower/dp/0061351229
I smiled and skipped it but now that I see your question, the timing seems right. So, why not see what does the author say? Here we go:

"Do dead people watch us shower? Does grandma know that I like to do that in bed? - Sure they do! And Grandma certainly does know. . . . They see us in the bathroom and they see us in the bedroom! But who cares? They’re dead! Who’re they gonna tell? Don’t freak out. The thing you need to remember is that they are not in the flesh—they remember the flesh, but it’s not of any concern to them anymore. They’re not judging. It’s not like they’re going, “Whoa! Has she got a big butt!” or “If I were him, I’da shaved that!” or “Holy Moly! Did ya ever see such a big . . . ?” Well, you get the point. The dead are not Peeping Toms—they don’t get any special thrill out of watching, it’s not entertainment to them—that’s thinking in human terms. They just look at it like human nature, like we might see two animals going at it and just look at it as animal nature. We might smile, or even laugh. But it’s not judgment. We don’t expect a couple of dogs or squirrels to be embarrassed that we see them doing what they’re doing. Yes, the dead certainly do see us in the shower or making love, but it’s just like we might witness an ordinary act of human kindness. We don’t judge it. We just smile and think, How beautiful. They are just happy that you are experiencing love or maybe just onenight- stand pleasure. They are happy for you. The dead are not nearly as stuffy about sex as some of us here can be—not even our dead Sicilian fathers!" And before you even ask the question—yes, they also see all our secret, sneaky behavior. They see us raiding the refrigerator and scarfing down the ice cream and the leftover lasagna when we’re supposed to be on diets; they see us picking our noses when we can’t find a Kleenex. Again, in their eyes, it’s just ordinary human behavior. No judgment. They also see us in the operating room and in the classroom and at our holiday tables. They enjoy with us all the events we celebrate in our lives and they also walk us through our sorrows and heartaches.

Despite what you believe, this medium has a nice message about being ok with it, and I hope you find it useful.

sometimes we think people are looking at us because in actuality we want to look at them. it's a psychological term called "projection". you may also have some form of paranoia like schizophrenia or bipolar, in which case you may need to see a doctor. try to breathe and relax. most people don't notice you.

Oh honey.... I've been through this. It's hell NEVER being comfortable, always being paranoid. You should really see a therapist. They're more qualified to help you.

I used to feel like that when I was younger. You should definitely go to a therapist if it is that severe. It's crippling, I know, but a therapist can help you a lot.