Our son seemed ready to potty train, so we got started last week. We bought pull ups and he gets an M n M after going to the potty. He was staying dry most of the time during the day and going poop in the big toilet as well. For some reason yesterday he decided that if he went to the potty, he had to sit there until a poop came. And he would only go pee if he had to poo. Same thing today, except he held his pee for so long that he peed in his pull up this evening. He pooped 3 times today and now we are trying to convince him he can go pee even if he doesn't have to poop. I have no idea what to do now. He will sit on the potty forever waiting for a poop to come, when all we want him to do is quickly pee before going outside or before dinner. He is taking a ridiculous amount of time to do anything right now so I know it's probably an independence/control thing. Hoping someone has some advice I can apply tomorrow. Thanks!

I plan on buying underwear in the near future but don't know if I should wait on introducing them or if they will help motivate him to pee more often.