Don't worry he will get there, he won't be in nappies for ever.
Having said that, he sounds like he's not quite ready yet.
Instead of full on toilet training, try familiarisation. Take (not ask) him to the toilet/potty before + after sleep and before he has a bath. Let him sit there for a couple of minutes, if he does something, praise him and celebrate with him, but if not praise him for trying and then leave it at that.
Once he realises that he can do it in the toilet/potty, he may be more inclined to want to do it more.
Ben 25/10/06 + Erin 10/9/08