It is normal for breastfed babies to go for even up to a week without a bowel movement. Breastmilk really is a superfood that gets digested so completely that there isn't much left to pass.
Most babies though are not in pain for not pooping and I would keep an eye of it, though small episodes of crying might just be gas or something other unrelated. If his symptoms get any worse or you are concerned definitely call your doctor. Sometimes babies can get bowel obstruction, it is not common though and completely unrelated to what you are feeding him.
You can help stimulate his bowels by giving him some "excercise": gently push his legs up to is tummy (knees bent like doing squats), bend his legs and move them from side to side, noting crazy, just gentle slow movements. Also give him a gentle clockwise tummy massage.
Make sure you keep feeding him on demand. I would not give water to an infant this young, breastmilk contains everything he needs.
Also don't think that giving him formula will help, it can actually constipate babies, especially if they are not used to it.
I also agree with trying a lactation consultant and finding a doctor knowledgeable about breastfeeding, our doctor was never worried about a couple of days with no BM and never suggested giving any suppositories or laxatives.
Good luck.