C.C.
What finally got us past the stage of my kids telling me right AFTER they went, was to have them go bare bottom! Skip the underwear, pull-ups and whatever else, and just have him run naked. This will do two things. 1) He will realize exactly what it feels like right before he goes, because he will actually be seeing himself pee (I know that sounds weird, but really, how would he know what happens? He's been in a diaper his whole life), and 2) it will force you to watch him very carefully.
When you think he is about to go, RUN him to the potty. When he makes it and goes in the potty, celebrate! When he doesn't make it, tell him very seriously, "Next time you'll make it to the potty." And then clean up the mess without any fuss. If you really stick to it, he will be potty trained in under 3 days. He may beg for his diaper back, but just very calmly tell him that since he is a big boy, he does not need them anymore since he will be using the potty now.
It helps if you don't take the process too personally. Think of it like teaching him to drink from a cup or eat with a spoon. It's a life skill that he needs to learn. Somehow in the 70's, this process became all about a child's readiness and self esteem and it was going to scar the child for life if you did it wrong, but I think that gives this process WAY too much significance. It's just another thing in the long list of things that he needs to learn. He's plenty old enough and you'll succeed!