Think I've changed a little this term

EDIT (10:37 PM) Discussed a bit with parents. Conclusion: Maturing, or age-gap between younger friends, or mood swings. Either that or study pressure.

I've been a little more different than last term, even though it pretty much just started.
I find Recess and Lunch quite boring, even with my close friends. I don't talk much now. It's quite silent, for some reason.
Things they find exciting, I respond to with an: "Oh yeah!" or "Haha, yeah.' even though I personally don't find it all that interesting.
It's like... the things they would say before would make me laugh or enjoy conversation. I felt like we shared a few interests, rather than none, which was good.
They like drawing (well, one of them does), discussing food/sharing it and stuff. Oh, not to mention the language barrier. I keep responding with 'Mm' or 'Yeah' as if I'm really listening or understanding
Though

I feel like I enjoy CLASS more. When I'm going to classes, I feel happy. I'm trying to contribute more in class discussions.
It wasn't like that before, not all the time anyway. but in reality, I'm not really finding it interesting. And to be honest, I don't find my year level so easy to talk to. Idk, I feel like they've all got fixed impressions on me, unfortunately viewing me as quiet and reserved or a bit weird for liking anime and such. I find the guys much easier to talk to, but all they do is play downball/other sport which isn't so bad but it's not so interesting. The girls? Yeah, I say hi every now and then or discuss stuff in class, but they're not really close.
So even if I tried to find some other people to talk to, it wouldn't be any better.
I hung out with the international Chinese students, because they gave me an opportunity to talk to them in Chinese and practice, discuss common interests, and sit down, enjoying lunch. Lunch is still enjoyable don't get me wrong, but for some reason it doesn't feel the same.

Not even sure why.
I've been working hard on my mathematics since I moved down a grade, and I guess that has been quite frustrating at times.
Even now as a type I feel like I should be doing work and not sitting here taking a break; even though it's far too late to do work since the brain doesn't concentrate so well at night.

Had a maths test today, not exactly sure how I went. Forgot two formulae that weren't on the formulae sheet. Oops.