My baby does not poop regularly and has gone a maximum of 5 days without pooping. Sometimes he poops 3 times a day and sometimes goes 3 -5 days. I was worried at first and called the doctor but she is not concerned. She said that as long as he doesn't seem to be in discomfort and as long as he is eventually able to go on his own without my helping (like with a thermometer in his rectum), then there is no need for concern. She said it is just his own pattern.
I'm not used to this because my girls pooped all the time. DS is eating great, growing well, and has plenty of wet diapers.