You should really talk to your school about a 504 plan, which is a national federal law, which helps out anyone with a disability including ADHD. They set different accommodations to a degree on helping any disabled student in k-12 discussed with the principal, counselors, teachers, guardian and students. Students with ADHD already have to work twice as hard paying attention and getting their brains to focus and take in stuff they learn in a regular setting, with online learning it’s very difficult. Please bring it up to your parents and teachers.
As for the medication. Are you taking it on an empty stomach. I know my child always feels that way when they do. Try eating breakfast before hand. You should bring it up to your doctor regardless.
Good luck and *fighting* ☺️