Potty Training Dilema

Pam for the past 3 days, has quit going potty in the toilet. She was doing soooo good. She pad even went "poopy" in the toilet last week. I'm so confused. She was doing great, was basically done. Now, she QUIT. She is using the potty pants like a Diaper. I cant have that. What do i do? sigh, so today i decided to try big girl underwear. We will see how that works. sigh, anyone have any advice?