Gluten help please

[PoptartPoptart]

Hi there,
I've posted about my DS before (he is 7). His tummy is always bloated (looks 9 months pregnant), he is more tired/lethargic than other kids his age and he only poos about twice a week.
I've been to the doctors twice now about this, and they did several blood tests including the TTG test for celiacs. It came back negative both times (I did not cut out gluten at all before the test). The doctor tells me there is nothing to worry about, but I am concerned as something isn't right. I've read lots of stories on here about doctors not being great with allergies etc, so I am wondering if I should take things into my own hands and cut out gluten from his diet for awhile to see if there is any improvement. So I'm after some advice please - If I do this, how long realistically will it take for me to notice any difference? Would cutting out gluten for a couple of weeks be long enough to see a difference do you think?
Also, if he doesn't have an allergy to gluten (as the blood test was negative) could he just have an intolerance to it? If so, would I need to cut out all gluten or just the obvious stuff like bread/pasta/cereals etc?
Thanks in advance for any advice

Personally I would push for a referral to gastro specialist before considering a gluten free diet. The Ttg test does sometimes have false negatives and therefore does not rule out coeliac disease 100%. A gastro specialist would be able to consider alternative tests based on your DS's symptoms. Have a look at the NICE guidelines for diagnosing coeliac disease (particularly point 1.1.18): publications.nice.org.uk/coeliac-disease-cg86/guidance

Just to clarify, the tests you are referring to are not for gluten allergy (there is no such thing as gluten allergy) but for coeliac disease which is not an allergy or intolerance but an autoimmune disease. It is however possible that your DS is gluten intolerant rather than coeliac and if you manage to rule out coeliac disease 100% then it might be worth considering a gluten free trial to see if that helps.

Thanks freefrommum, the problem is that our doctor was very dismissive of my concerns and was very exasperated with me when I insisted on the blood tests. I do not think she would be open to a referral tbh. She even said that DS was one of the healthiest boys she's seen in a long time, which is great to hear, except she really couldn't explain why he gets the symptoms I described. If I cut out gluten from his diet myself, how long before I saw an improvement/any difference do you think? Would his bloated tummy reduce significantly within a few days if it is the gluten that's causing it?