A while ago I posted on here about ds's suspected food intolerances (gluten, milk and soya) and lots of you were really helpful - thank you. (And also sorry, because I never came back at the time to thank you.)
I've been to the GP, as you advised, and seen the paediatrician. She is holding-off on the coeliac testing for now, as ds is already on a gluten-free diet. Eventually I know I'll have to reintroduce it, but we thought we'd get potty-training sorted first.
Anyway, thanks for all the good advice - much appreciated!