my baby was the same, right from the very beginning (the only panicked phone call we made during the first-time-parent-newborn-stage was to the doctor when he was three days old, freaking out that he hadn't pooped in 30 hours. of course, he went literally 5 minutes later). then he had the normal newborn-shart in every diaper for 12 weeks, and the minute he turned 3 months old he started going 10 days between poops. the first time we asked the ped (at 10 days) she suggested a suppository - we waited one day, and he went that next day. then it was 10 more days til his next poop . . . 14 days another time . . . then he went 21!! days without pooping. on the 21st day i thought i better go buy some suppositories, but of course he finally went that very day (and like twice a day for the next three days). every time, i would start freaking out by the end, but every time, he ended up going without any help from us, and it was always kind of peanut buttery/toothpastey, but never hard or pellety. i basically just kept an eye on his urine output, his tootiness (if he was tooting, i felt secure that there wasn't an obstruction), and made sure his tummy was still tender - if he had stopped peeing or felt swollen around the belly, i definitely would have tried a suppository and taken him to the pedi.
he's 7.5 months now and has been trying solids for the past month and a half - he usually goes every 2-5 days now. on his longer stretches, he gets a little cranky towards the end, but he's always had perfect poop once he does go. i've learned that this is just normal for him. i would say, just keep an eye on his urine output and make sure his tummy isn't taut or hard.and certainly call your doctor if you are still feeling uncomfortable about it.