Should my baby poop after every feeding?

No. Stooling patterns for infants are very different from adults. Some newborns poop after every feed (yes that can mean 8 times a day!). Some breastfed babies, however, absorb all the nutrients in the milk and can go up to a week without a poopey diaper. As long as your baby is gaining weight well, his stool is soft, there's no blood in the diaper and the stool isn't a white color its probably ok.
No. A young baby usually poops after every feeding or after every-other feeding (averaging 3-4 poops a day). As the weeks go by, babies tend to poop less often, some twice a day while others once every-other day. As long as a baby is normal in eating, growth, and development; and does not have constipation, bloating, or tummy aches; the number of poops per day is not very important.