Boy, was I in your shoes.
But like everone else has said, your professors are trying to weed people out who really don't have the drive or desire to be a nurse. It takes a really special person to be a nurse, it isn't a job everyone can do.
If you really want to do this, don't let them force you out. If anything, forget about earning all A's, I gave up my stright A's when I enterd my program, to continue that in my program would have been suicide as I am sure it is for all the others reading this message. I had doubts but have made it to my final year and couldn't see my self doing anything else but nursing, it is wqell worth the work. Along the way you learn what the BS in BSN stands for too
But really, I hope you don't let all the crap push you away from nursing if it is your calling, good luck to you!