[¯|_(ツ)_|¯]

Hey,

I want to start out by saying that this is not your fault. You should be able to wear whatever type of clothing you want without someone looking at you, and just because someone is a guy doesn't mean they have the right to continue looking at your body when it is clearly making you uncomfortable. Also, you're still a minor and no adult should be looking at a minor like that.

Are you able to talk to your mom about this and let her know what is happening? You can let her know that you've noticed your stepdad has been checking out your body and it is making you feel really uncomfortable. You can ask your mom to talk to him about this and see if it changes his behavior at all.