Hi Charm Bracelet,
First of all, it's ok to be confused. It happens to the best of us, especially when dealing with the male species. Just kidding - no offense guys
One thing that you said really sticks out in my mind the most. That is, "I find myself attracted to him now whereas before I didn't." In my honest opinion, this is a classic case of a challenge. In other words, we want what seems to be impossible at that moment. First of all, I think what you need to do is be honest with yourself. Do you really have feelings for this guy beyond friendship? If you do, then consider pursuing him. If you don't, then weigh how much this friendship means to you.
It sounds to me as though his friendship means a great deal to you considering how he makes you laugh, etc. Now, to answer your question regarding why he has become cold and distant from you all of a sudden, there could be many reasons. Sometimes guys withdrawl if they too have feelings & are unsure of how to sort out those emotions. Another possibility is that he is going through something in his life right now. He might be withdrawling from everyone, not just you. If I were you, and as easy as I know it is to do, don't take it personally, ok hon? If you know for a fact that you didn't say anything offensive to him, it probably isn't you. So don't blame yourself for something that is out of your control!
I think your next step is to just say to him next time you see him, "Hey, I don't know what has caused you to become distant and it really doesn't matter at this point, but if you need me, I'm here. If I said something to make you upset, I'm sorry...I didn't mean to hurt you." See if he opens up from that comment. If he doesn't, then just give him time. Let him come to you when he's ready. I know it's hard to just sit back and do nothing for a while, but it might be necessary in this situation. Also, I know you're shy, but guys DO like confidence. So bring out that side of you (practice if you have to) and show him that you enjoyed what you had & you'll really miss it if you have to get used to not having it any more.
My best wishes are with you. Good luck!