I like this guy, but....?

Ok, so I like this guy alot! He is my boss at work. I flirt with him every chance I get, and he flirts back even harder. But I saw him flirting with another girl, and while he was doing it he looked right at me and put his hand on her shoulder. Then later he was flirting with me harder than ever. I dont know if he was just doing to see if it would make me jealous or what. So my question is, how can I show him that I want him? but i want to do it subtly,