To hopefully ease your mind a bit - my daughter had extremely similar circumstances from about 2 months till 7 months (very sick, LOTS of respiratory involvement, ER trips, hospitalizations) with no known cause. She was being treated with EVERY respiratory drug known - nebs, steroids etc etc - but still wasn't any better. Eventually, our doc started to talk CF... she was sweat tested and was negative but was still having crazy issues. Finally, an ER doc suggested severe GERD and began treating her immmediately - it made a huge difference! We then confirmed using a Upper GI (easy-peasy!). Due to some other issues, we also had to have a endoscopy to verify structural completeness in her GI tract. This was HORRIBLE - she had to be put under general anesthetic and intubated (they secure the airway of kids that young for this procedure) - she reacted horribly to the intubation and was in the recovery area for over 2 hours and we could not see her. It was one of the most stressful experiences of my life! Words of wisdom - treat with the medicine and hope it clears or ask for an upper GI, not a scope. HTH! I know this can be so stressful...