My son's poos are really really pale, almost white. is this a problem?

Possibly: It may be normal but it's also possible that there could be a health problem causing it. I would suggest having him checked by his doctor; bring some of his soiled diapers in with you to show his doctor as well.

Usually not: Transient pale-colored stooling is observed in healthy infants and children not too infrequently. Pale stool close to chalk in jaundiced newborn or child could signify serious liver pathology.