Wow, you could have been describing my son 6 months ago! Actually, I posted the same question back then, I think.
What worked for us was to see this potty-training thing in steps. So great, he's mastered the naked step. Now it's time to do the underwear step, and after that, the pants step.
First, I made a chart on a big piece of paper and taped it to the side of our kitchen island. It's near the downstairs bathroom, so it made sense. HEre's the thing with the chart, though. After a few rows of orange boxes that my son would be filling in with stickers every time he used the potty, I drew a simple picture of his reward. In this case, it was new underwear. I already had a package that I'd bought really cheap, but he thought they were awesome and we talked them up. With my first son, he got to pick his own out at the store.
After the little drawing of underwear, there were more rows of boxes (this time brown) to fill in with stickers, and at the end was a picture of a tent and some trees and the moon. His reward (which was generously suggested and donated by Dad) was a camping trip. He did that with our first son and wow, they really responded! Of course, now it's cold, so that might not work, but I know that my boys would be just as excited to set up a tent and camp in the family room with mom and dad.
And after the underwear boxes were filled up, I told my son that the rules were different for filling up the brown boxes. He had to be wearing his underwear all day to get a sticker. If he was naked, he wouldn't get stickers. We never had to withhold stickers for being naked, because he SO wanted to go camping!
My doctor also suggested that we try not changing his wet underwear. If he pees in it instead of in the potty, that's his problem. It is cold and wet and uncomfortable, and eventually he'd realize that dry is better. He said to block him into the kitchen or somewhere with hard floors (easy clean-up) for a whole day (which requires a big commitment on mom's part) with the potty seat in there, and he'd get it. We never had to do that, and never really could since big brother just started school. But it's an idea! Maybe you could do it on a Saturday?
Good luck, it's hard to know what to do in these situations.
BTW, my now 3 1/2 year old has a few accidents still for reasons we can't really figure out. They all happen in clusters, so he'll go for 3 weeks with no accidents and then one day he'll pee his pants 4 times. I don't get it, but still, he only wears diapers at night, and I can take him places in underwear. Yay!