If you haven't already (and if you can afford it), get the most comprehensive blood panel your doctor is willing to order.
Two main benefits:
1. You'll discover something is off.
Which will let you take investigative and/or corrective action: adjusting your diet, supplementing with vitamins or prescription drugs, taking further tests, etc.
2. If at some point later in life something goes wrong and you get blood work, you'll be able to compare those results to the tests you had before the problem started.
This should help narrow the hypothesis space.