My neighbor is a peeping tom?

The guy is like 40 and it creeps me out. I live with my roommate. The first time when I realized he was watching me was when I was changing into a bikini one day and I saw him looking. So I only change in the bathroom now because it has no windows and I put curtains in my rooms, but I still see him look through his window when I look outside. Is he trying to catch another peek? My roommate is guy so our neighbor doesn't peep on him. The guy has a teenage daughter too who's close to my age. I'm scared for her. What do I do to make him stop?