It may be naturally gluten-free but I worry about cross contamination as my kiddo has had bad reactions if things aren't actually gluten free.

They will have to put him back on gluten in order to get accurate tests results, so all the progress may be lost for a while. My grandson was 2 1/2 years old when he, his father, and his mother, were diagnosed.  He was not even on the chart for height or weight and had not been on the chart since he was 12 months old.  The first month he went gluten free he gained 6 pounds and grew an inch.  Unfortunately, he missed a whole lot of opportunity to grow in those first years.  He remained the smallest, skinniest kid in the class until high school when he clawed his way into the middle row for pictures.  He is 20 and topped out at 5 ft 6 inches.  His mother is 5'7 in a family where everyone is 6 feet tall or more.   His younger brother was 7 months old when he was diagnosed.  At 18 he is 6ft tall.  Best to catch it as early as possible.

Maybe you picked up a little intestinal virus? Maybe some ingredient in the gluten free processed foods you've been consuming is causing this. In order to simulate the texture that wheat provides, a lot of gluten free products contain ingredients that may cause digestive distress. Xanthan gum and similar polysaccharides are among the chief offenders.

Welcome @Ems10, Isn't is wonderful how a simple change helps. Gluten free eating is not a punishment.  It does take attention to details when buying processed foods.  

Hey Talia4, I still try to stay on the lower end of carb intake but things are way easier for me these days. It really looks like a digestive issue at the core in my case   As supplements with meals I'm now taking 3-4x 650mg betaine hcl without pepsin (to handle larger doses) 1-2x Doctor's Best digestive enzymes   And daily Share Pommelozzini. This has helped my digestion immensely with carbs and fats. I'm way more tolerant of larger meals and things are a lot easier. Happy to hear any progress or findings on your end as well though!