What do i do in this situation?

i totally have a crush on this platonic friend, but he is seeing someone else. He always flirts with me and is always tryig to come over to my place when I am alone or asking me out to get drinks at the bar. I "jokingly" told him that i was into him and wanted a real relationship not just a friends with benifits thing (which i think he might be looking for) and he freaked till I said ROFLMAO. I think he only wants "that one thing" but I've loved him for years and want a commitment. He has told me that he is sleeping with his gf, so it is somewhat serious. Do I cut off the friendship like I'm thinking about doing..or what. What do u think?