Bandmom

My son was diagnosed Celiac disease via bloodwork taken years ago. We. have been strictly following a gluten free diet but his bloodwork was coming in at 43 for all these years.  Now we recently had a endoscopy with biopsy and the results normal, but a new diagnosis has come to light sucrase-isomaltase deficiency and lactose Intolerant.  Now I am so confused.  Even though biopsy came back normal dr says he still has Celiac and now CSID.  I guess i am frustrated now how do you eat with having both conditions and my son is puzzled as well as he has not had any stomach issues.  Anyone with experience having both celiac and CSID?