I went to a alternative doctor, who did a bloodtest and it came back that I was Gluten intolerant. I think, by eliminating gluten for a month or two and then re-introducing, you can tell if you have a big reaction or not. Is it's celiac disease I think you will even react to spores of gluten, so I would try that first.
Does it really matter if it's coeliac disease or sensitivity? If you really want to know, you have to get a gut-biopt but then I think you have to be eating gluten regularly. And even then the tests can come back negative, while you might feel better without the gluten.
I do feel a lot better if I don't eat gluten (and sugar and milk products too actually). I once had a day that I really didn't care, well, let me say that the toilet and I got very good friends that day... Spores of gluten I think I can handle, but perhaps my body thinks differently. Maybe I don't recognise the symptoms as symptoms, because I have eaten gluten for about 39 years, just started 2 years ago eating glutenfree.
See my comment above to the other responder but in response to your question as to how gluten sensitivity is diagnosed, it's often with a food tolerance test AFTER all appropriate tests are done for coeliac and they can't come up with a diagnosis. Because then it genuinely is just a sensitivity.