M.S.
My son cried for months on end and the doc said it was colic... well it was actually internal ear infections that no one could see on the ear drum. I forced the doc to finally have his hearing tested, even though he was given a clean hearing bill in the hospital, and found out that the fluid behind his ears was so bad that he was actually deaf!
So, look into ALL possibilities because babies don't cry for no reason...
Ear tubes made him the perfect baby boy he was trying to be!
good luck...