My contact lens diameter is 14.5. Does it matter if I buy new contact lenses with a diameter of 14 if everything is the same (power, bc, etc)?

Probably not. It should not make a big difference but the diameter of a lens can change the fit. In general, you should stick to the lenses prescribed by your eye doctor. If you want to change lenses for whatever reason, it is best to see your doctor and get a new prescription to make sure that it is safe for you.