How to keep my 2 yrs 8 mon boy to stop going number 2 in his pants?

My son has done really good on peeing on the potty. He goes when he needs to, and everything is ok in that department. The problem is he won't tell us he needs to go number 2. We ask and ask and he just says no he dosent need to go. Then not even 2 min later he comes in just stinkin to high heaven. What can I do to help him out? Is he afraid of the toilet? This has been going on for a couple months now. Thanks for your imput.