Exam in two days, can't study?

-OMG, I am so panicked i cannot even type properly. I have two days to study for a biology exam, and every time I sit down to study i can't process anything i read. i keep confusing myself & i've been at this for 2 hours now. i've tried writing things down, saying things out loud, but i immediately forget what i've read and i have to keep going back. I think it is a lack of motivation, i don't feel like i have to study but i KNOW I have to study. this situation is really shallow i know, but i don't know how to handle this. when i am motivated, i feel pressure. also i don't trust myself. how can i trust myself? i think trust is the other issue. even though i know it, i can't trust myself to tell myself i do know it. university will look at this mark and its already so low, please help me. i feel pathetic begging for help on a forum but desperate times ...