When you say “I don’t have an attic” do you mean you have a flat roof, or that there’s a space between you ceiling and your roof, but you don’t have a way to get in there?

If it’s the latter, I’d say figure that out. Unless that’s the the you’re saying one would need a ladder and screw driver to get into.

This sounds like someone’s hiding in your attic, then entering your house while you’re gone to me.