I am an adult and things have not gotten better. If anything, they’ve gotten worseTry cardiovascular training or simply long walks. If it helps, take someone with you.
You don't have to do a lot, just stick with what you have started.
I've also been bad at maths. Math teachers are often under the delusion that anyone can follow their explanation and who can't is lazy (or stupid). Some speed through lessons like dogs hunting rabbits. So it was sometimes up to youtube to teach me maths. I actually started to get better at it after school, during professional training, with no pressure on me.
I can relate to the bullying. I suffered through this for all of my school years. I simply could not figure out how to deal with my peers. Teachers also ignored when someone got bullied, as a result I ended up being the lone wolf.
It will get better in adulthood. Whenever you find yourself in a group setting, remain polite, ignore quarrels and fight for what is important. I've been treated unfairly but showing them the cold shoulder is pretty effective
And not all people are assholes but it does happen.
The problem with people like us is that others will immediately recognize us as the odd one out. They don't know how to deal with us, we put them off. Two people trying to communicate with different languages.
I had people describe me as unempathetic, cold and aloof. I'm none of those things.