sorry he's having troubles that way

I don't have any real trick for you. My DD has a slow metabolism and right from the start, her poops were fewer than my fast metabolismed boy. He pooped all day as a baby (probably didn't help I was on domperidone for supply) but her, she pooped once a day as a nursling and then when I started solids, she slowed right down! straining etc. So then I realized that, well, duh, I was giving her rice! so switched to oats with the odd brown rice cereal but it took me after giving her the 2 first fruits to clue in (seriously, takes me a while to process stuff. LOL no pun intended!!) her first 2 fruits were banana and apple!
ok, the BRAT diet when you have the runs is: Banana, Rice, Apple, Toast. no wonder her system was stopping up.
So when I switched to oats, I also added puréed prunes (man, I loved that cereal!) she got prunes in her cereal every two days and that helped her be regular (poop once a day, sometimes every 2 days and yeah, seldom soft.
Now, as a 4yo, I give her the extra vitamin C multiple Flintstones (the only kid vitamin I could find that uses real sugar and not some fake sugar). That girl doesn't eat any fruit! (ping! another grey hair just popped out) she'll eat watermelon--sometimes. sigh. and don't get me started on vegetables.
so all that rambling to say, extra vitamin C? you can find chewables but the problem with those is that they stick in the teeth and erode the enamel. So maybe if you do give that, give it at the start of a meal where the other foods might help "clean" his teeth.
I know that too much vitC gives very loose stools... but I think you have to eat A LOT. Never affected me when I was popping extra when I had a bladder infection but then, I too have a slow metabolism.
good luck and keep us posted.
jm

me:43, DH 44
FSH 26
DS: born by c-sec Apr15'03, 9lbs5oz 41wks gest. (after 4 years of ttc, starting in 1998)
DD born by c-sec Oct 13 2007, 8lbs13oz 39wk gest. (after just under 3 years of ttc)
~~DS was conceived naturally the cycle following a cancelled DE IVF, using my good friend's eggs. She was on the verge of hyperstimming.
~~DD's nat conception I attribute to using OPKs like a crazy nut, eating grapefruit daily and using preseed. also 5 cycles of TCM ending 2 cycles before that lucky cycle.
~~~~~~~~~~~~~~~~~~~~~~