Potty Training

So, Potty training didn't go as well as I had hoped, and we decided to put it off a little bit. We still are not putting him in diapers, but we have decided to go to pull ups, which he thinks are underwear. The problem we are having is that he is telling us he has to go potty as he is going, not before he goes, so he is already wetting by the time we get him there. He gets the panicked look and then starts going before we can stop him, and I can't figure out a way to get him to understand to tell us before.
We put a pull up on him yesterday afternoon, while we were at my aunt's for the 4th, and he still told me when he went. This morning we tried the regular underwear and it was the same thing. I asked him if he wanted to put on diapers and he said no, which is good, because I really didn't want to go back to those, but as long as he thinks that he can't go in the pull ups, and that he still needs to tell us, I can't see that there is much harm in it...
So my official vote? 3 day potty training didn't work... 5 day potty training didn't work either. But he has learned some bladder control, he has learned to tell us when he has to go, and he has learned how to physically go on the potty.