What Causes Watery Stool Along With Acid Reflux?

My grandchild has watery stool with what looks like small lumps of cottage cheese in it. He poops about 6 times a day for the last 2 weeks . But hasn t lost any weight has actually gained 2 pounds..he has suffered with acid reflux and had a milk allergy. The formula he is on is nutramugin.. I took him to the dr this morning and now I have to have his stool tested. I m kind of scared as to what they may be looking for.. Any advice please.