I feel my dad checks me out? Why do i feel this way?

When ever i wear shorts, i wear long knee high socks since i have a big birthmark that lows my self esteem, and so i hardly wear shorts but when i do i feel dirty in front my dad, i feel he just looks at my butt and thighs n legs... And just by walking around him i feel nasty, i often times see him checking out girls MY AGE (13-17), or women around there 20-30s, and my mom even catches him just drooling over em n dosnt say anything, and i feel gross just seeing him do that... I want to tell my mom how i feel but then she's going to tell my dad what i said and he'll get mad... What should i do? I mean some guys say there isnt anything wrong by just looking but he's 40! Or am i just paranoid or something? Please help me