3yo won’t poop in the toilet !!!help!!

has anyone had trouble with their 3 yo pooping in the toilet??? my son was doing so good pooping in the toilet and just about 2 weeks ago didn’t want to poop in the toilet anymore and absolutely refuses to he only poops if he has a diaper on he goes pee completely fine in the toilet and goes when he needs too he’s so good with telling us he has to pee and poop and wears underwear all day and night but when he has to poop he asks for a diaper and will cry and throw a fit until he has one on or he holds his poop in :/ i talked to his pediatrician about this issue and she said that he either figures it out that holding his poop in hurts him or just give him a laxative and then he has no choice but to go in the toilet or in his underwear😅 has anyone gone through this? any advice ?