What I do when I have a non-pooping kid is the "I Love You" tummy massage. You massage the tummy in a clockwise, circular motion for a bit, then you take your fingers and press gently to do the "I Love You." It's easier with a drawing to look at, but I'll try to explain. You begin with your fingers (I use the index and middle fingers together), and you make a line (the "I") from the bottom of the righthand (your right hand) ribcage down to the groin. Then you place your fingers below the far left corner of the lefthand ribcage and make a line across to the right and down to the groin again (the upside down "L"). Lastly, you place your fingers on the left upper groin and make an unpside down "U" shape that follows the path you just traced for the "I" and "L." You repeat this over and over until you don't feel any gas bubbles moving around anymore. I like to do it on the changing table, it seems to be the most comfortable for both baby and me. For my older dd, I do it on the bed. It's basically a massage that traces the large and small intestines in the direction of the colon. It gets things moving. I find that my girls will poop within 12-24 hours of the massage. OH, DON'T FORGET TO USE OIL OR LOTION.
Good luck and I hope your baby poops soon!