What should I do...?

Long post ahead. I enjoyed writing it.

A guy i've been classmates with for 3 year, a guy I have a crush on the moment we played a game together on the first day, but later on, became casual, no feelings whatsoever. Never talk to each other, other than group related project subjects.
We both were never interested in each other. I would never have thought that he would fall for me, 3 months in a new environment, new school, not classmates but we have the same Private Study set together.

It all started when I noticed that he waited for me by the shadows, the other side of the road, when he saw I was the last one to go home during our class reunion. It was late at night and I thought, oh, how nice of him. Ever since then, he started to to exist more and more in my life.

With one of his friend always hinting towards him whenever i'm around, teasing him when i'm near him. During those time he would always smile shyly and maintain his coolness.

He is shy, he doesn't talk much, and has a poker face anywhere- the only time he'd smile or laugh or anything is when he's with his friends- I could not guess his expressions.

We have PS together and we're always in the library, I wouldn't say we sit with each other, more like it's either he's on the table in front of us, or a table near us where he would always face my way. He's always in my line of sight, everywhere that I go, he's always there. I could sense his presence.
In the library, he would always have his bag on my bag, or near my bag. It's always like that- after PS we would be packing and he'll always be next to me when that happens.

One time I overheard a conversation, among him and his friends. We were in an event where hes sitting with his group of friends and I sat with mine, both facing each other.
I wasn't talking to anyone that time and I heard his friend saying something like "oh yeah, (his name) and this girl--- her nickname, library girl right? blah blah"
I couldn't get the rest but I definitely heard that one.
At that moment, I was sure. I'm pretty sure that girl was me.
Considering the fact that he looked at me when my friends had this group photo.. both looking away afterwards but ended up looking at each other again.

We're both 17. I'm very shy, I don't talk to lots of people- especially boys. I have my own circle and so does he. I admit, i'm pretty hard to approach, however, if he talks to me, I would not mind that at all. (In fact, I literally talk to anyone that talks to me- I don't ignore anyone at all). I don't know why, I feel like theres this thing where people think that shy people won't talk to you back or something like no, I would be more than happy to talk to you. I'm just shy, to make the first move, thats all. I guess thats the problem though, he's shy too, so it all ends down to either me or him, to initiate the first conversation.

I want to talk to him, but at the same time I feel like it might not be a good idea. Maybe he'll lose interest in me then, if he finds out that I might be too... different than what he expected. or something.

I just don't get why he would fall for me. I don't think i'm beautiful or anything, but it's not like I look bad either. I'm pretty ok. But I just don't get it. Why now? He's going to move to a new school this August (where theres lots of pretty, and very very social people there). Why would he like me when he's about to go away? Why would he appear in my life- make me feel something and just disappear?
Why is he doing this to me...?

Is it selfish of me, for wanting him all for myself but at the same, would not want to be with him?
No reason why, I just had a mindset that I might find someone better in the future - which I think is unhealthy but, I don't really know what I want.

It's not like I don't like him, but I'm just not ready for anything serious.

Please give me your thoughts. I don't know what to do.

Thank you in advance. If you have any questions about me or him, I'll gladly answer!!