Hey! I hope this message gets to you, since the thread started awhile ago.
We all get into those moments when we're stuck. It happens, and if someone told you it never happened to them - well unless they're a robot, it will happen to them and it's just a matter of time.
Studying is all about motivation and sometimes it's hard to maintain that motivation and focus when there are many stress factors. What you need to know is, that what you're doing now is not indicative of how you will be in the outside world. Some of the worst students in school are the best pharmacists in practice.
Have you considered new studying habits? How about group studying, or tutoring? You need to try new ways of studying. When we get older, it's difficult to just sit in class and absorb the material. Passive learning is for younger children, when they just absorb by listening or watching. As grown ups, we have to find other means of learning. I remember using color pencils and drawing every orgo chem reaction with it. That was how I managed through that class. I even bought clay and started making models.
How about reciting your notes? If you speak your notes out loud, it helps you process the information too. Often times when you write it over and over again, you see it on paper but it's not really realized in your mind. Make the words real by speaking it.
You are having a mental fatigue moment, it's not a shut down unless you give up. So, don't give up and keep on trying!