Over-stimulation can be too much sensory stimulation such as sights and sounds and/or it can be too much cognitive effort, over-stimulating the cognitive processing.

You are early in your recovery. If you can reduce stress and over-stimulation, you will enhance your recovery. Sitting for a lecture is likely over-stimulating. You should ask your school's disability department if they can provide a note taker to help you with lectures. But, at the least, talk with your disabilities department to see what assistance they can provide.

My best to you.