I think A&PI is the most difficult class of the pre-requisites. Mainly, because it's all new, it's accelerated, and on top of that you have the anxiety, perceived or real, of having to get an A.
We all know that once you are actually an RN it's not the grades that make you a good nurse.
You can probably still get into a nursing school with a B in A&PI. But, my advice is to get that A (because it sounds like you still can) and get rid of the doubt surrounding a B. You don't want to be looking back at that B and wondering if it's good enough for the next few terms before you apply.
Do whatever it takes, it's only 6 more weeks to the end of the term. You can do anything for 6 weeks. Consider using the tutoring center at the times when A&P instructors are there, schedule one-on-one's with your instructor, form study groups with people you know are doing well in the class, etc.
You can do it KMDGuy!
PS: If you end up with a B you can always retake the class for a higher grade. Perhaps with a better instructor ) BTW who is your instructor?