I Am A Graduate Student And Am In An Advanced

I am a graduate student and am in an advanced pathophysiology vourse. I am having the hardest time concentrating and am afraid I will fall far behind. I spend so much time reading and re reading the same information because I cannot concentrate. My jumps from topic to topic so much I cannot retain the information. Is there any short term medication that I can take to help me? I have no medical problems and am
Not on any medications.