What am I to him?

I fell for a guy who is the most adorable thing to me. Everytime we are together (usually with other people around), he is extremely attentive to me, even lifts my head to put his pillow beneath it, brings me a gl of water without me asking, asks about about my favourite food, says we should "hang out" in Paris together, says I'm amazing, says we will cook for me, etc. He has a long term girlfriend in America (he is UK), but sees her twice or three times a year. He doesnt know I fancy him, he just thinks we are very good friends, and we are. The other day I invited him for dinner. we acted weird, it was the first time we had been alone. He later told me he felt nervous around me and didnt want to feel as if he was cheating on his girlfriend. (we didnt even touch! nothing happened). He told me he loved her very much. So why does he act like that with me? why does he hold my hand, tells me those things he should be saying to her? What does he really feel for me? please help me, please