It's okay to be undecided! It sounds like you are willing to listen to your instincts, which is the best way to go with decisions like this. Even when things don't turn out the way we expect, they take us on a path that we would not otherwise access.

I got a master's after college, and I knew the very first day that I had made a colossal mistake. It was not for me. I stuck it out because I was already enrolled, and though I didn't love it, the parts that I did enjoy took me to my real career choice.

Good luck exploring your options. Is there any way you could shadow a nurse for a few days? I know that when I 'tried out' my job (teaching) by observing, I knew right away that I would like it. Testing the waters that way can give you an idea what a job really entails on a day-to-day basis.