I know this is overasked, but i really need some help! does he like me?

I really like this guy- let's call him Mark. I asked him to Sadies and he said yes. That night, he wrote something on my myspace about how we both like the same quote. Then, we didn't speak for about a week except for some casual hellos in the hall. I always wanted to say something more, but i was too scared. I am always nervous to even say hi to him, so sometimes I don't when I see him in the hallway. But, last night we talked on AIM for an hour until he had to go because his dad made him get off to go to bed. The conversation flowed and it wasn't awkward at all. Also, today after school we hung out in the computer lab together for about 40 minutes. When i walked into the lab, I didn't say hi, but then I asked him for help on some math homework. He came over to help me, and then showed me a video of his on youtube. Then, he signed off his other computer across the lab and came and signed on to the one next to me. He helped me with all my homework, and we were like joking around.