3 yr old wont sit on potty/ toilet

[Tortycat]

Ds is 3 and 4 months and getting nowhere with potty training. He knows when he needs a wee and poo and can tell me. But he wants to do them in his nappy. If i leave him with nappy off in the morning, when he needs to wee he'll ask for his nappy. If i dont give him one he'll get upset. I just give him one now as i want to keep it all positive, and when i didnt a few months ago he got constipated which i think was from witholding. Ive tried potty or seat on toilet, choc mice (his favourite treat) if he sits on it, picking pirate pants, story book (pirate Pete's potty), but to no avail. He can't explain why he doesnt want to sit on the toilet/ potty. He watches me and dp on the loo, and likes flushing the loo, but wont sit on it. Any advice????

Anyone??

Hi Tortycat,
I've had a slightly different experience with my son but some common ground. My son would wee but not poo on the toilet. Also he NEVER said he needed to go. He would either go to the potty for wee or poo in his pants (no, zero warning).
We started training when he was 3.3 and after 3 months of this regime I was getting really annoyed/frustrated/ready-to-murder-the-child). My son started withholding poo (like yours) so I called the health visitor.
They didn't have a miracle solution but what we did helped diffuse the tension and later on he made progress. At 3.10 he finally went to poo on the loo (as well as tell us he needed to go).

So. For one month, we used a pompom jar. If he used to potty or toilet or told us he needed to go, 1 pompom in the jar.
However the jar comes with strict instructions:
don't use it to reward anything else (only for potty)
NEVER take a pompom away, once it's earned it's earned (you're trying to reinforce positive behaviour)
if there's a poo in pants and it's practical to do so, show your child how you put the poo in the loo
NO threats or bargaining. Potty=pompom, accident=clearing up calmly and silently

After the month mark my son was still not pooing on the loo but he had stopped withholding it in. A few weeks later he started sitting in the loo saying he was pooing but nothing was happening. He also started asking questions about where the poo was (ie in his tummy and coming out from his bottom at the back unlike wee). This all coincided with a huge growth spurt.
He still prefers pooing in his night nappy first thing in the morning but if we're out and about, he now tells us and goes to the toilet to poo.

My view is that my child needed to be a little older because he needed to understand (intellectually) more before he felt more comfortable.

Hope this helps

Sorry I forgot to mention buying dissolvable sacks you can put directly in the washing machine (like they use in hospital). This should reduce your level of stress about cleaning the mess.