I went gluten free seven years ago to help with inflammation in my body and also to alleviate bowel issues. Recently, I tried to introduce it back into my diet and I have obviously gone about it all wrong. My stomach has been hurting for 5 days now and I haven't consumed gluten for the past two! What is the best way to reintroduce gluten and why does my stomach hurt so bad?"
With this level of detail, I can only offer hypotheses for you, but here goes: Prior to giving up gluten 7 years ago when you were experiencing 'bowel issues', had you been properly tested for Celiac disease? If not, we cannot exclude the possibility that you might actually have it, which could explain the residual stomach pain even two days after abstaining from gluten-- and possibly some 'inflammatory' type symptoms from seven years prior, depending what those were. If you were my patient, I'd be working with your doctor to have some genetic tests run (HLA types) to see if it's even genetically possible for you to have Celiac disease. If you don't have either one of the two celiac genes, its highly improbable (less than one in one thousand chance) you could have the condition. If you did have one of the genes, we'd be talking about whether you wanted to suffer through a 4-6 week gluten challenge to confirm the diagnosis, or just assume you're Celiac and part ways with gluten forever. With only three days of wheat eating in the past seven years, it's unlikely that conventional blood tests (tTg-IgA) used to screen for Celiac disease will be reliable right now.
If your doctor did rule out Celiac disease years ago (or can do so with gene testing now), though, then it's more likely you're reacting to the fermentable carbohydrates in wheat (fructans) rather than the protein in wheat (gluten). Recent studies show that this is the case for the vast majority of people without Celiac disease whose gastrointestinal symptoms improve on gluten free diets. If you fall into this category, the gluten-containing foods that will likely agree with you the most are those low in fructans: sourdough bread made from wheat (white or whole wheat) and spelt bread (or spelt sourdough bread!). Soy sauce and conventional oats, both of which likely contain some gluten, should also agree with you as they are low in fructans.
There are certainly other medical possibilities if these hypotheses don't pan out, but they're much rarer. Good luck!