Is your precious angel not sleeping after a good feeding as nature intended? Give him ten minutes. He may be unable to sleep because of the sensation of an impending crap so mighty that nations will tremble before it.
Bonus advice: Change the child as soon as the post-pooping rumbles have died away before he falls asleep. Mine passes out as soon as he's done, if it was in fact a giant crap keeping him awake. Then I wind up staring at him, trying to decide if the never wake a sleeping baby rule should be violated. I know I should, or else use a hose to clean him and the bouncy seat at the end of the nap. But he looks so peaceful that I just end up blogging about a rhino stampede-halting stench.