Re: Could this be Celiac Disease?
AuntieLeela has some excellent advice -- it's definitely worth it to get tested for celiac disease, but make sure that you keep eating gluten (wheat, rye, barley) until the tests are scheduled. The blood tests measure antibodies to gluten, and if you stop eating gluten, these antibodies (if they exist) will clear out of your blood and your test will show negative.
It is possible to become gluten-sensitive later in life. Many doctors think that if it isn't present when you're a baby, then you don't have it. This isn't true -- many people have varying degrees of sensitivity. And since it does appear to be an autoimmune disease, it sometimes shows up later in life when some stressor triggers the response.
Another thing to consider, after you get the test and if it turns out negative, is to start your own gluten-elimination diet and see if your symptoms get better. It took me several months to find a doctor who was willing to consider the possibility that I was sensitive to gluten, and by that time I had figured out that my body was reacting every time I ate wheat. So I had already started changing my diet by the time I found a cooperative doctor, and my blood test as well as the inspection of my upper intestines shoed no evidence of gluten intolerance. So I am not "officially" gluten intolerant, but it is very plain to me that gluten triggers autoimmune responses in me. I am well when I avoid gluten, and my body reacts when I (very occasionally) eat some.
And some people simply don't produce the responses to tests that result in an "official" diagnosis, but they find that a gluten-free diet helps anyway.
And, of course, it may be something else entirely that is causing your symptoms. I do hope that you are able to track it down.