Can i use nystatin cream usp 100,000 grams per unit for a vaginal yeast infection? just on the outside or can i use inside? and can i use it pregnant?

Safe: because nystatin is not significantly absorbed into the body when applied vaginally, and because its highly selective for fungi (it works as a porin, opening holes in cell membranes) its generally safe. However, products such as terazole that come in special applicators may be more effective, and still generally safe.

YES: It will not harm pregnancy in cream form.