My 6 year old passes very large stools so big they do not flush, but lately they are yellow in colour and he states his stomach is burning?

Large stools: His "stomach burning" may be pain due to passing of large stools. Stool may be yellow because of food he has eaten.

Time for consult: I would have him seen by his PCP and evaluated for chronic constipation/stool retention. If your PCP is unfamiliar with the issue, contact a pediatric Gastroenterologist or developmental pediatrician.The various problems that lead up to this symptom are complex, and often take months and years to resolve with proper help.