Delayed diagnosis and misdiagnosis are very common in Celiac Disease.
http://jccglutenfree.googlepages.com/delayofdiagnosis


As others have said, though, misdiagnosis or missed diagnosis is very common. For example, I was dx'd with BFS, BPPV, idiopathic PVC's, and had a wide ranging symptoms...but eventually I found all my symptoms were related to a B12 deficiency, and 95% of my symptoms resolved after correcting it. All of my idiopathic, benign, and somatic conditions disappeared.

My advice to those who remain undiagnosed and want to find answers is to keep on searching and networking with others who share like symptoms~ on forums like this!

Cara