Celiac disease, its linked to an increase in various intestinal cancers and also lymphoma, amoungst other illnesses. It's easily treated, but sometimes hard to detect. I literally was told it was in my head, other times I was told it was food aversion. When a dr finally listened to me, he went back over all my blood tests through the years and found the problem.

But my point is that some dr's will write off your physical symptoms as a mental problem if you have a previous history of mental illness, and more so if they are failing to detect the problem. I should add that this wasn't a few months of seeing dr's for the same problem. It was actively trying to find an answer from them for roughly 6 years.