Potty training: My 3+1/2 year old son will use his potty, but only as long as he's

[shaunabanonna]

nude! Help/Suggestions? If there's nothing touching him in that area, he will go to the potty by himself and do his thing.. I've tried training pants, potty training diapers, underwear, a progress chart with stickers, incentives (i.e. when he gets 3 stickers, he gets a small toy), and still, I'm not getting any further. I feel as though I don't have much more time, that he's getting to be too old for this, but I don't want to rush him. Any ideas would be so appreciated, I'll try anything at this point, hahaha!