I really reallly have a thing for him. What should I do?

I only had one cl with him. It's a half a year course and all the sudden, we started talking(flirting) on the last day of my first semester cl. Somehow I really have a thing for him. Which I never would see myself liking him. But he's in my homeroom and we only see each other during lunch. Ironically, he sits back to back to me. My guts tell me he is interested in me but never knew how to really express it the right way. He wants to look but sometimes doesn't want to. The thing is every time he was around his close friend, he wouldn't have a chance to at least stare at me and have a conversation. I know he misses those good old times when we had fun in one cl. Everyday, he puts me in a smile. No one ever did that. He tried to make me laugh when I was down. And today, we had schedule changes, we were in our homerooms and all the sudden, all i hear is him talking to his close friend about that cl how he didn''t want to be in it. But I know it was sarcastic, he just didn't want to tell the truth to his friend. And that's funny because he couldn't stop staring at me while me and my friend were talking about our new cles. To conclude this essay, I really am interested in him. I just don't know what to do. Do you think he is interested in me and wants to try to have a conversation with me? I never felt this way and I'm not sure if it would be creepy to ask for his number from one of his friends. What should I do? Helppp me.