DS crying each nappy change. What to do?

[PoisonMountain]

Really, really upset. Doesn't want to wear his nappy. Especially for the night nappy. He is nearly 3, yet never tells us when he needs the potty/toilet. He will go before bath time. But, for example, the other night he did his poo, a small wee and told me he was finished. I left him in the bathroom to go and wash out the potty and told DH to watch him. By the time DH had got there he had sat on the base of the potty and filled that with a huge wee. Another time (i was timing it and asking him every 30 mins, he wanted to wear pants) he went on the potty and not 15 mins later he had wet the sofa. He seems to have no idea when he is doing a wee or needs to go to the toilet. Then he gets terribly distressed and upset if he has an accident. He cried for 20 mins solid the other day (poo leaked out of his nappy, not his fault at all, just the way he was sitting) and asked to go to bed. I've never seen him so upset :(

Sometimes he says he wants the potty so I take him, then when we get there he says no potty and refuses to go on (full on screaming, thumping head on the ground), then refuses to let me put his nappy back on (fights and kicks me).

He is at crèche today and tomorrow, but I need a plan for Wednesday. Do I stay in with them, take him every 20mins or something (but what when he refuses to go?) or just pants and keep asking him, or just pants and let him decide himself?

[PoisonMountain]

Oh, and I don't tell him off if he has an accident, I just clean it up, clean him up and if he gets upset tell him that he needs to tell us next time he needs the potty and we'll take him, it's ok and give him a big hug.