Can you pinpoint WHY you're doing so poorly in the nursing classes? Could it be that the material really doesn't interest you? That you don't like studying sciences (or therapeutic communication, or whatever it was you were taking)? Do you have larger issues going on in your personal life that make it difficult to learn at this time? For instance, are you suffering an illness, going through a break-up or caring for a sick parent?
Most of the disciplines you've listed are also going to require intense study. Physical therapy, for instance, requires graduate education. To be a dietician, you need to understand chemical reactions in the digestive system, nutrients in various foods, organic chemistry, statistics and other "difficult" subjects. If those subjects don't interest you, you're going to find that course of study difficult. Even chiropractors have to study the skeleton and musculature. It involves a lot of rote memorization and it also involves graduate studies. If you're flunking out of nursing school
, you won't be a good candidate for admission to graduate school.
There are health care jobs you can do without graduate education. My sister-in-law is an X-ray tech; specifically a mammographer. She loves her job and the people she meets. The X-ray techs who come to our ICU to do portable CXRs believe they have an interesting, challenging job. Respiratory therapists can become licensed with an associate's degree. There's still a lot of anatomy and physiology, but colleagues who have left nursing school to go to RT school tell me that the courses are "easier." (Of course, "easier" is relative, and what is easier for some might not be easier for others.). Check into phlebotomy, medical technology, pharmacy assisting and coding.
School is easier if you're really interested in what you're studying. I'm not sure where your interests lie or what kind of classes you find easier than others, but once you figure that out, your course will be a lot easier to plot.