Will prednisone 10mg for 2 weeks cause low potassium? i have chronically low potassium but doc isn't worried??

Unlikely: Prednisone can lower the potassium concentration in part by causing fluid retention and dilution of the serum potassium. However, the problem is dose/duration dependent, so a short course of a low dose of prednisone is unlikely to cause a problem. You don't mention that you're on a potassium supplement, but, if you are, you certainly need to continue it.