Feel like school's caging me in...?

Today, was my third day back to school. For the last week-and-a-half I've been off. The snow kinda got to me, making me feel...not myself. But for the last days I've been back to school, i've been fine...until now. Today, I walked to school (30-35 mins) and had to stay in as the snow's poses safety risks, which i'm fine with. But when I sat down, I talked to my friends for a couple of minutes then just...froze. I felt as if everything was out of focus. Then I had a...daydream? I thought I had ran to the toilets, covered my mouth and screamed. I later realized I hadn't when I forgot where I was. I hadn't moved. The lessons in that day also seemed really hard. It was like climbing a mountain trying to concentrate.

My mam kinda unintentionally told me what it might be when she mentioned "fresh air". I've kinda had none of it this whole week-and-a-half, plus these days i've been at school. I told you how long it takes to walk to school, and it takes (on average) 100 secs for me to get to the car. 36 mins per day.I can't go out as everyone's too ill, and even if thy do come out, they always end up going in mine or someone else's house.

In conclusion, advice would be appreciated. But i'd prefer just an explanation to what exactly it is. If it is from lack of fresh air, what is the specif problem called?

thanks for any help, John.