Natalie,
Firstly, don't give up! You are currently passing your assignments and although the marks could be higher this is something you can build on with a little guidance/advice. I mentioned on another thread that I don't believe a good academic essay writer makes a good nurse. If you would be willing to share the tutor's feedback here or by private message I would be happy to provide some advice that may help you (and others) in the future.
Whatever you do - believe in yourself even in these tough times and remember that the skills you bring will make you a great nurse.
Cheers,
David