need some advice ladies

My DS is 4 in sept and has been TT for a while now day and night but in the last few weeks he has started to poo in his undies often.
He will poo on a potty and in a toilet and is good at going to the toilet to do wees so I know that he isn't scared to do and I am at a loss as to how to approach it.

I have tryed...

Telling him that big boys go on the toilet and that it is not okay to do poos in his undies.

Encouraged him to take a bit of responsibilty for it, well his dad actually, he got him to help hold the undies while he rinsed them and talked to him about it at the same time. We also get him to use a flannel and soap to wash himself down in the shower after.

As I mentioned before talking about it at the time and also casually other times.

There is nothing that comes to mind that is not confronting that I can try, I am out of ideas. I don't want him to think that he is naughty.... even though it does really annoy me.
Do you have anything that you have tryed that works?

A sticker chart? Gets a sticker for the days he does it in the potty and when he has enough gets a reward.

Thanks ladies, I can't believe I didn't think of a sticker chart huh

I will get some cool car stickers for him and give it a whirl smile

I hope it works for you. I was going to suggest a sticker chart too. My DD1 had some major issues with poos in the last 6 months when she previously was doing great. I think she must have hurt herself on the little toilet seat/step we were using on the big toilet. She started just using the toilet without the seat and would get 2 stickers for a poo and 1 for a wee.

This has worked so well for us and now she is going no problems. I made my chart so that when she got to the end of a row of stickers (10 stickers in the row) she would get to pick her own treat at the shops. smile