Toilet problems!

My daughter is 20 months old. About two months ago, she started telling us when she needed to do a poo. (i.e. she'd come to us, point at her nappy and say"poo poo") So we started putting her onto the toilet. She cried and screamed so much that we just took her off. Five minutes later she had done it in her nappy. Over the next month or so, she kept telling us when she needed to go, and we put her onto the toilet (and potty) and the crying and screaming would continue, only to have her do it in her nappy as soon as it was back on. She would sit on the toilet/potty for a while and "push" but would never actually do a poo. Now she no longer tells us because she knows we will sit her on the toilet/potty. I've put it down to the sensation of having nothing under her bottom when the poo is coming out.
The other thing is she also tells us when she is urinating, but only when it is actually happening.
Any ideas on what to do?

Make sure you praise her when she tells you she wants to poo or wee and don't get upset at her if she does it in her nappy...even though it is quite frustrating! My son too used to crack up when I sat him on the loo, I used to put him on the loo even if he said nothing of needing to go and I made sure he sat there, whether he liked it or not, for about 10 mins! I made sure I rewarded him even just for trying at first, then only when he actually did something, even if it was only a little trickle! I had him toilet trained just after his 2nd birthday! I hope this helps.

Best wishes.

thnx for the advice mum78. I have gotten into the routine of just sitting her on the toilet for a few minutes several times each day. She's into "being naked" right now, so isn't minding it as much as she used to. She still pushes and doesn't let anything out though, so we're still working on that bit! But she's more than happy to sit for a little while to get a little treat afterwards! smile I'm hoping to get her toilet trained just after her 2nd bday just like ur son was. Keep ur fingers crossed!