It is very common for breastfed babies to go a long time between poops, but usually that pattern doesn't start until the third month. In a newborn, it's concerning, but not alarming. The main worry with no-poop at this age is that the poops are the main way you have of knowing that baby is getting enough milk. My DD1 was an infrequent pooper, right from her first week, and it worried us, but what we noticed was that she was also putting on weight at an amazing rate-- she went from 7 1/2 pounds at birth, to 12 pounds at two months old. So we stopped worrying. If I were you, I'd be keeping a close eye on weight gain, and otherwise not worrying a bit. If the weight gain slows down too much, then it's time to think about ways to increase the amount of milk baby is getting.
Another comforting sign is if, when the poo DOES come, it's ample, and soft, and the color is somewhere between yellow, yellow-ish brown, or yellow-ish orange, with no more than a tint of green. That would be very reassuring.
Another reassuring sign is alertness-- a newborn that's not getting enough milk will often become extremely sleepy. Baby would sleep for very long periods, and have trouble staying awake long enough to finish a feed. If baby is feeding fewer than 10 times in 24 hours, I'd be concerned.