Am I not girlfriend material?

Dear Ryan, I recently moved to Hawaii where I was pursuing a job. A friend of mine was already living there and offered me a place to stay. I already had some feeling for him and it only got worse when we started living together. We do everything together (even though he has a girlfriend) and a lot of people often comment that we are like an old married couple. I cook dinner for us after work, he calls me just to say "hello" and we work out together on the weekends, among other activities. He has a steady girlfriend, whom he cheats on constantly, but my feelings for him have gotten much stronger. I am stuck in a rut and have tried dating other guys, but find myself thinking about him the whole time. Help! Signed, Confused in Paradise