My 4 Year Old Grandson Has Diarrhea At Least 3

My 4 year old grandson has diarrhea at least 3 times a week. For the past couple of weeks not and then says he feels like throwing up, but never does. I have him on a probiotic daily, cut back on diary products.
I mentioned the symptoms to his pediatrician during his checkup last week, but didn't feel it was any concern.