Is it unusual for someone that is being treated for c-diff not to be able to eat certain foods? should i be on a certain diet?

Yes and no: You are likely being treated with Flagyl (metronidazole). For that, you should not drink anything with alcohol in it, including cough medications, while you are taking it. After you are done with treatment and cleared of the c-difficile, you should be able to eat anything you want.

Low fiber: With c diff your colon is very limited in its ability to pull the water out of your stool which is the main purpose of the colon. So the more i digested food that makes it to the colon the worse things are. Fiber is not digested so it will increase the problem. Things like fruit and beans citrus and other green veggies that are usually great for you may be a problem now. Ask your doc.