3.5 year old regression

[Jacoba]

My little boy (3.5) was showing all signs of readiness at 2.5 and reliably went to the potty and was dry in the day, minus a few accidents for several months.
For the last few months though, I can see he’s wet himself (a small amount, so he must be holding the rest in) when he’s playing or when he comes to sit on my knee. I’ve tried his favourite dinosaur underwear for when he does his wees on the potty or loo.
I do gently remind him, but he’ll only go when he’s absolutely desperate and already let half of it out. We’re changing trousers 5-6+ times a day. He knows he can get more trousers so he just doesn’t seem bothered tbh.

Get a big supply of ugly trousers and pants that he doesn't like, and have him wear the ones he really loves first thing in the day. If he has an accident he now has to wear the ugly ones. And make him have to undress himself and put the clothes in the washing machine etc, so it is way more trouble to wet himself than go to the toilet. If you come and undress and redress him while he's playing then he is incentivised to not use the toilet much as he misses out on less playing by wetting himself than going to the toilet

I just came on here to post the same thing!
DS will use the toilet if I tell him too, but left to his own devices he will start peeing and then run to use the toilet...it's becoming a real problem at nursery I've tried sticker charts and rewards and nothing is working, I'm just hoping he grows out of it at the moment, please let me know if you have any success!

Clean him up really slowly, so take him up to bathroom, strip him off, go finger some clean trousers, stand him in the bath to sponge wash, get him dressed again (taking your time about each step). Strech it out so he's alway from playing for at least 10 minutes, that way it's more worth while for him to stop playing for 30 seconds to have a wee.