Can I full time study?

I am a new nurse just starting working 6 months ago using the OPT. My application for greencard was filed in Jan (Vermont), and I-140 got approved in the end of Feb. My I-485, EAD and AP is still pending. My OPT will expire in June, by that time I cannot work anymore unless I get the EAD.
I don’t really like the unit I am working right now, because the coworkers are very picky on me and always give me the hardest shift since I am new. Many patients in our unit have psych problems which always made me feel crazy, because of the language and culture difference. I am thinking about either changing jobs or going back to school. However, I am not sure whether I can change hospitals after I-485 pending for 6 months. So I am thinking about going back to Nursing Master program (Nurse Practitioner).
MY QUESTION IS: Can I full time study after I-485 pending for 6 months? And what will be my status if I full time study? F-1?