Only you can decide how much effort or stress you can tolerate in a day. Your brain is telling you what its tolerance level is. Your school should have a disabilities department that can provide a note taker for lectures. Lectures can be very stressful. Any time you start to struggle to understand the lecturer or to read a line of text, that is your brain saying "I have had enough."

Pushing through usually means you will extend your recovery. There is no free lunch with PCS recovery. Your brain needs less stress. You need to figure out how to moderate your activities if you want to improve.