Another Breastfeeding related question...

My 10month old daughter (T21) has always suffered intermittedly from, what I believe is, abdominal pain.
It is usually accompanied by arching, straining, tense stomach and wind(flatulance). It has often disrupted her sleep and is exacerbated by lying horizontally.
She will often wake at night in pain and I usually resort to breastfeeding her to facilitate passing wind.
I have had her tested (bloods) for coliac as there is a high incidence amoungst DS population- tissue transglutaminase came back negative- although I understand that this does not necessarily rule it out, especially in this age group.
Previously I found evidence that gliadin does go through the breastmilk so I went gluten-free for a couple of weeks. I did see a reduction in pain and her constipation resolve but not perfect. On assumption of wheat back into my diet the symptoms did not clearly reverse so I questioned my hypothesis.
Recently though, she has been waking numerous times per night - so I thought that I would try wheat-free again when I realised that she had considerable pain after consuming spinach. I am now wondering if she is sensitive to oxalates?? (found out that wheat germ and bran contain also)
Is there any merit to this theory?
Would they transfer throught the milk?
Any other ideas?
Ps- my mother says that I was very sensitive to what ever she ate and she had to delay the introduction of solids