Not pooping regularly. Feeding normally.

Hi, My son is 4months old, weight is around 7kgs. Birth weight is 2.7kgs. From last 1 month he is passing motion either after 1 week or 2 weeks, we have been to Rainbow Hospital, pediatrician said he is perfectly alright and prescribed us to use Neopeptine drops and half rectal suppository if he is not passing motion for 10 days, Last week we have tired to insert half suppository and while we are trying he passed the motion, so till now we haven't used any suppositories. And for the current status again he didn't passed motion for 1 week. Can someone please help me why my son is passing motion after week or 2 and when ever he passes stool it is very soft. Apart from this he is passing urine normally and having BREST FEEDING normally.