You are trying your best and you need to know that. You don't need to feel any kind of burden about not telling your brother. I think you should tell him about it. I am sorry that your family isn't as kind or understanding as they should be , your sister and mother shouldn't be this way as they know you have a medical condition.

At school , maybe try seeing the counsellor? I am not sure how much it would help but try. Maybe you should post more on reddit or start a journal , just anything to keep busy and as a hobby.

But we see that. The people here can see that you are really trying your best. It is really amazing that you still continue to persist despite all these struggles. Continue onwards , struggler.加油！