Does he like me or what? I'm confused...?

i like this guy a lot and we hangout at school. The problem is he has a girlfriend. He knows I like him and he flirts with me. My friend used me as a model for her photography class and he begged to see my pics bc they were a little naughty. I finally gave in and showed him. He looks for me at school and we talk. He even gave me a ride home a few times. Also, he even tries to sit with me. He texts me and asks to see racy pictures. He told me he wants to marry his gf and plans to propose later this year, but he fulled around with me without her knowing. Does he like me or what? we have known each other for years and he says he is not using me. I feel weird just asking him how he feels because i know her loves her. We are perfect for each other and talk about almost everything. I feel bad for his gf but i wish he were with me. What do I do?