I really like my best guy friend?

we were in the same summer health/pe class and he's friends with my friend...so we talked. And he's such a sweet person and everything seemed to work out perfectly. I didn't even know him and my friend were great friends. Anyway, I still like him. And I'm just acting as a sister to him and he's like a brother to me. But I like him more than as a brother/good friend. I don't want to ruin the friendship, but I don't want to miss out on a chance. Sometimes he acts like he likes me, and sometimes he acts like a brother. My friend said that he started assuming that I like him...but i didn't want to confirm it or deny it. So now he invited me and my friend to the movies with him. And we're all going (as friends) but I still like him. Again - Cheesy moment! - I kinda like imaging that him and i are walking around the mall holding hands or going to movies together...and now it's all here in a few days. It's funny how it all worked out. But i like him more than a friend but i don't wanna tell him and risk making everything awkward. So what should I do? Also, he one time said he would go out with me(a few days ago) but i kinda laughed it off cuz i am VERY shy. So what should i do? Thanks!