Sometimes, in order to reach a definitive diagnosis, other disorders/diseases have to be ruled out first. If blood work and scans are normal, perhaps try different doctors.
Well maybe your disease is just psychological or that you don't really have anything wrong with you. Try out bikram yoga and all of your feelings or pain will go away.
First of all, try explaining to the doctor in details, about your problems. Or perhaps there's nothing wrong with you. Sometimes, psychological stress can produce sensations of sickness on patients.
There can be a few reasons why doctors cannot find what is wrong with a person. Are you sure that you told everything to you doctor. Some little symptom that you think nothing of can possibly point the doctor in the right direction.
There could be a number of reasons. It is possible the condition you have has not been researched very thoroughly. If you are experiencing chronic pain, investigate Fibromyalgia.
If doctors have checked your health, done tests and found nothing, you probably are healthy. Is your thought illness caused by your thinking. Talk about anxiety with your doctor.