Potty Training Woes

So Cole has been pretty much completely potty trained for like a month or so now, which is very exciting!! However, here in this last week, when we are at home, he has been pooping his pants. I am not sure what happened he has always went poop in the potty before and now all of a sudden he decides not to! When I ask him why he pooped in his pants all he says is "yucky mommy, I pooped in my pants"...I encourage him to poop in the potty and he says "I poop in the potty mom" and gets all excited but when it comes down to it...nothing...hopefully this is just a stage and doesn't last long!