ina, i would pursue this until you get a definitive answer. go get a second, third, etc opinion if need be. there are competent docs out there and many who are not.
my son was born with a rare disease. he was very ill from birth. i took him to a diagnostic hospital well known and they told me "he had no illness, i was just an over-protective mother". i had given them the family history of this disease also. turns out that is exactly what he had.) i finally was so desparate that i scheduled to see a new doc. told him my concerns for my son. i said if you're not interested in helping me with my son then don't waste my time. not too tactful but i was so over it and scared. you keep pushing onward to get to the bottom of this. please keep us posted.