Aren't you a witch Sabrina? Just make some kind of potion to help with your exams... sorry.
Why don't you consider a foundation year? Most foundation year entry requirements are around a C grade, there should be courses related to biology. use that as a safety net tho.
For now, try the best you can on your remaining exams and taking plenty of breaks so that you aren't overwhelmed with anxiety. Some form of medidation may help as well. In the end of the day, whilst its good to give importance of your exams, they aren't the end of all means. Try to do past papers in an exam setting as much as you can to condition yourself, to avoid those silly mistakes. gl