I had this problem and sometimes still do. Bear will eat, burp, settle and fall asleep. I start to do my daily chores and then hear **pffft!** and then screams of pain coming from my little mans crib. Before you run to the store and buy a wedge to keep your baby elevated, sleep positioners so he doesn't roll off the wedge and a bottle of asprin to keep your head from exploding try this out. Under your baby's mattress put a 3" 3-hole binder...voila! you've created a wedge for about $3.00 as opposed to $20-70 (yes...$70!) This keeps baby elevated just enough so the bubbles rise to the top instead of cramping up his poor little belly. If your baby likes to slide down the wedge or does better sleeping on his side, take a regular sized bath towel fold in half length wise and roll either end toward the middle. Stop once there is a 6" gap between the two rolls. Place baby in the middle so the rolls are from his armpits down (this way he doesn't sleep with his face in the towel-not safe) if you're near a Wallmart or Target a bath towel is about $5-7.00 no need to be fancy, any towel will do. The thing I don't like about store bought sleep positioners is when your little one (god forbit) pukes or poops on it, it's almost impossible to get it out. A towel you just un-roll it and stick it in the wash with the rest of the dirties!
Now for just about $10 you've helped your baby get a good nights rest...well...a good two hours at least!
If anyone has thoughts suggestions or questions feel free to comment or e-mail me at firstname.lastname@example.org