Hi A.,
Poop is always such a concern with our little ones! As mentioned, every few days with a BF baby can be normal, as can several times a day. I can see why you'd be worried with the signs of discomfort you are seeing in your baby, though.
Keep up drinking lots of water yourself - that's great! I agree that you might want to offer the breast more often and see if that helps. Also, when my daughter went through a bit of this same problem when she was an infant, the pediatrician did suggest a wee bit of juice in some water (a tiny amount of juice, like a tablespoon maybe - mostly water) and offer that 1x a day in a bottle or soft sippy (depends what your baby accepts and can manage). We did this on occasion and it did help (it wasn't something we did all the time though). We avoided apple juice and usually did either prune juice or white grape juice in the water (studies have proven white grape juice is gentler to the system than apple juice).
Being EBF (exclusively breastfed) is the ideal diet for your baby up to a year old or more, so that's super that you are doing that for him! Go, mama, go! As long as he is getting plenty of mama milk, he will grow and thrive. Other foods are really only needed for "eating practice" and fun until our babies are at least a year or more. Whenever you do decide to introduce first foods, I'd stay away from cereals as they can be very constipating (they are highly processed and there's no natural nutritional value there for baby anyway) and try things like pureed sweet potatoes, pumpkin, avocado, squash to begin with. Those are appealing, nutritious and also help with regulating poop. Incidentally, bananas are constipating, as is processed applesauce, so I'd avoid those for some months once you do start solids, till your son gets well established with his digestive routine, whatever it may be for him. When we did give our daughter applesauce, I always mixed it with pureed prunes to counteract the constipation factor, and she loved it (of course she loved straight prunes too, but they gave too much of the opposite effect! LOL!).
Best of luck in helping your little one get comfortable pooping again!
Blessings,
S. M.
PS I have the cutest magnet I got at www.cafepress.com...
"I make milk...what's your superpower?" :)