a regular doc will be able to assess you and point you in the direction of a specialist.
potential lifestyle/nutrition issues are far from likely to be addressed down the mainstream avenue.
you will need to seek alternative/complementary assessment if you are interested in that kind of investigation.
here's some reading to help you decide if it could be a worthwhile course of action: regimens-f22/
(most times you don't need a diagnosis to take action with nutrition.. testing if great but putting a nametag on the illness is not really the point.. one thing though, you should be aware of whether you have any genetic issues that affect how your body handles nutrients, whether your on meds for which certain things are contraindicated, etc)
my approach: no meds so far - just nutrient-dense anti-inflammatory whole foods, and supplements where needed
info: www.whfoods.com, www.nutritiondata.com