See someone, and don't stop until you find someone that you feel is really listening.
MIL went through this with DH - took him to the GP over and over, even the paed wouldn't listen, wrote his diarrhea off as gastro for weeks on end and he just kept losing weight. Then, middle of one night, she cracked it, had had enough and took him to the Children's Hospital, where someone finally paid attention and he was diagnosed with Crohn's disease.

So do what you have to do. And don't let up!