What to do when dad has watched me undress?

So Im a pretty smart person at reading people and their body language and all.. and I got the hint that my brother was watching my change and undress in my room when I was 14 through the cracks of my door. I was of course right. Then when I was 16, I didnt go to school one day and it was just me and my dad home. I got the hint that my dad was watching me because he would say something to me through the bathroom door (and he never did that) and i didnt hear him walk away, and sure enough he was watching me. I have looked through the crack of the door countless times and seen him trying to watch me naked getting into the shower. Now, I finally got the courage to tell me stepmom and she believed me at first but my dad denied everything and now she, nor ANYBODY in my family believe me. Im 17 now and they still dont, because, of course, they will listen to an adult before a child. Now this is my father and I dont want to hurt him but he has hurt me mentally and Ive developed extreme paranoia and anxiety from this. Im not the type of "weirdo" that asks all this stuff online, but I have realized I have nowhere else to turn. I dont know what to do and I cant find information on how wrong this is because well, dont all guys want to see females nude? I just need opinions on what I should do in this situation because this is my FATHER, I just dont understand how a parent could do this to their child. Just please help me....