Is this illegal

So this is a hard one but is it illegal to have a hidden camera and watch someone even if your name is on the lease. My ex and I split but we are on the lease together and I suspect he has a hidden camera watching me to see who comes by. He is currently staying with family until I move. Is this illegal or no? I still feel it’s an invasion of privacy but sense he’s on the lease wasn’t sure if it’s legal for him to watch me and pretty much do whatever he wants. I am moving soon but hate the feeling I’m being watched.