Hey sorry to hear about how things are for you, I definitely think you should talk to someone at the school, the teachers are there to support you, especially if you've got ones you trust. If not you might be able to talk to a school nurse or a counselor.
People shouldn't look down on you for a medical condition that cannot be helped, and you should NOT blame yourself as it is not your fault but you might be best going behind your mum's back to tell someone you trust at the school, that should be a lot of weight off your shoulders and the school might be able to get something in place for you to support you, including providing resources so you can continue studies at home when you can.
Hope my thoughts on the matter helped, and I hope that you feel better in yourself soon