Potty training

Has or does anyone else's toddler do this? We are currently potty training and the only time my daughter will use the toilet is if she is Commando (wears no underwear) if she has on underwear or a pull-up she will just say " I have to pee pee" and pee on herself. If she is Commando she 100% uses her toilet with no help. She just turned three.