3 year old wont poo on the loo or potty - wee fine - any idea

[dscully]

No idea why my ds 3yrs 2 months wont poo in the loo or potty, weeing fine, late to do it but all good, just pooing in pants, doesnt want to put nappy on, tried laying nappy in potty. Has done one or two when just couldnt hold on any more, but usually in pants, even when been on potty less than 1 min before. Have tried reward, bribing, being disappointed, not allowing to lay down (stops the poo from pushing down) He is really miserable lots of the time now and a different boy once it has come out. Help

Thanks for that, he definately knows when he wants to because he gets upset, holds his bum and walks in circles before asking to lay down to stop the feeling. He can also hold it for more than a day so has control, it just seems odd as he has always been regular, never constipated or hard poo which would hurt. Am at a loss.