Havent managed to read all the replies, so apologies if Im repeating what others have said.
We have just come out of a 6month nightmare trying to potty train my son (turned 3 in September) Like yours and others, the weeing was no problem at all, took to it straight away, no interest in potty. Had very few "wet" accidents. But the pooing was another thing all together, we didn't manage one in the toilet at all for the first 5months, and we tried EVERYTHING, poo goes to pooland book, praise, rewards, absolutely everything. I would sit with him for ages in the bathroom coaching him, and he would push and push and go red and say "I don't need a poo" then we'd go put a nappy on him for bed, and he'd do it straight away!!!
Anyway, as I said after trying everything, I gave in and phoned the health visitor, she said to basically stop making a song and dance about it, no fuss no huge praising, no sitting and coaching him through it, no offering gifts/chocolates etc. In fact just don't react in anyway to the poo issue. She said if you know when in the day he is likely to poo (which we did, it was usually just after dinner) to put him on the toilet and tell him it was time to do a poo, then sit and read a magazine, or if you felt comfortable leave him in the bathroom. She did say he's not going to just do one straight away but it was important we stopped making this a big deal (by this point my son had seen me VERY frustrated and upset by the whole thing, cleaning poo every day is not fun!)
So this is what we did, it took about a week before he did a little poo!! The first time he actually pooed in the toilet, Id left him in the bathroom just to get on with it. I did go against her advice and jump and sing for joy when he did it, and he did get a lollipop, and he was so so pleased with himself. This was about 3 weeks ago now and since then all poo's have gone in the toilet! touch wood it continues! He will now just take himself off for a poo, but we all have to go and look coz hes still very very proud of himself!!
For what its worth, Im not sure he recognised the sensation of needing a poo, I think it took him a while to get used to something coming from there (sorry tmi!) and what the sensation was. Now he stands and gets a look on his face and says "I need a poo" and I think that literally is it, he knows he "needs" one!
I also think not making a big fuss really really helped, leaving him or sitting and reading a magazine in the bathroom just took the pressure off him I think to perform??
Hope this helps in some small way, you have my upmost sympathy coz this above everything else, breastfeeding, weaning, sleeping etc has been the one thing that has brought me to my knees!!
I wish you lots of luck, and speaking from experience, you will have a little boy who poos on the toilet soon, I promise!!!
K