DS wont do "poo" in the toilet


Hi all,
My DS is 3 and 4 months and has been toilet trained during the day since Sept but he still refuses to do his poo in the toilet. When he needs to go i have to put a nappy on him so he will do it. How can i get him out of this habit? Also i havent even tried to train him during the night either should i try yet or leave him till he masters the other one???
It'll come in time. Andrew has had trouble with this for months now - he was fine for ages & then for no apparent reason began trying NOT to poo & smearing his pants, or worse still letting go completely in his pants . There's only so much of that you can take before you begin to go mad! KateB suggested putting him in boxers & unfortunately that wasn't the magic bullet I hoped it would be. If I leave him bare-bottomed, he goes to the potty straight away. Kate's logic was that boxers have that bare feel .
Anyhow - we've been searching for the 'currency' that will matter to him & make it worth his while... and I hope we've found it - skittles . He disappeared into the living room yesterday & was 'sitting' suspiciously. I reminded him that when he poos in his pants we get upset & it's a lot of cleanup, but when he poos in the toilet or potty there is huge excitement & celebration. A minute or 2 later he trotted off upstairs & called us to clean his bum. Totally clean pants too!!! He got a skittle in each hand (as required!). About 2 hrs later the little maggot asked if he did ANOTHER poo would there be more skittles? Well we had to say yes & lo, he went again. On the 'mummy & daddy' seat on the loo, not even using the small seat.
I don't get it but I'm certainly not going to argue with him!!
As for the night stuff- that will come when it's ready too. Andrew has been dry by night for months, whereas there's a 6yo girl up the road who still wears pull ups. You can't force it.
Jamiesmum - my DD is the very same. She was 3 in July, and has been trained since last May, but still won't poo on the toilet. She has been constipated on and off and is afraid it will hurt, and I'm finding it very hard to break the association between poo and hurt. I've tried bribery like PL, but to no avail yet.
Sorry, no advice, just to let you know you're not alone
Its very frustrating, but hang in there!

Thank you for putting such a fine point on it . I told Aileen I'd collapsed to the point of bribery & she told me it was 'positive consequences'.

p.s. it took us ages to find the RIGHT currency. We're not new to bribery - but it's taken a while to find what would actually bribe him, kwim?

For More:

DD waking at night for hours.
car seats
Hepatitus B innoculation?
Feel stupid asking but....
First week over for SAHD
OMG The terrible two's are well and truly here!!
BCG Mark reappearing