child pant wetting and soiling

Our child is 5 and has been potty trained for 3 years. He is wetting his pants during the day and I don't understand why. He also "rests his poop". This is where he deliberately holds it so he doesn't have to go. We try to get him to go and praise him when he does. This has been going on for so long now that it worries me that he is hurting himself, it can't be good for his intestines. We try to remind him to go, we offer rewards if he goes without wetting/soliing each day - we've actually developed a chip system that if he doesn't wet or soil his pants, he earns a chip to use toward things he wants. We've made charts with "star" stickers and if he goes 7 days without wetting/soiling he can get a prize. We always tell him how proud we are when he "poops" on the potty. Nothing seems to work. He's at a point that he can't go more than 2 days without an accident. We have tried to let him know it's okay that he had an accident, we love him and we ask that he just keep trying. Are these actions psychological? Does he do this because it's something he can control? We have asked why he doesn't want to "poop" on the potty and he responds that it hurts his feelings, NOT that it hurts to actually go. What can we do? We feel like we have tried everything and it doesn't get better.