I work at a school in the USA, I don't know how schools in your country are set up. Does your school have a counselor who you can talk to? If so, can you confide in him or her about your condition, take some information so they can learn about it and help you through these first weeks? You may need to modify your schedule a bit, plan rest times.
Be sure you get your sleep - that is so important - even if you don't study as much. If you are too exhausted you won't recall the information you've sutdied.
Hugs dear, there are others on the board who are close to your age and who will have good coping ideas for getting through the school day. I'm sure they'll chime in soon.