Progesterone after BFP?

I had an IUI on March 27 and have been taking progesterone since. Today I tested positive on 2 hpt and it is my last day of progesterone. I tried to contact my doctor's office today to find out if I should refill my prescription and keep taking the progesterone until I can schedule an appointment to confirm pregnancy and the receptionist said the phone nurse was very busy and may not get back to me today but I should schedule an appointment as soon as possible. Should I go ahead and refill the prescription and keep taking the progesterone until I can get an appointment for confirmation? If you need the progesterone to sustain pregnancy will going a few days without cause a miscarriage?