First-Nancy congrats on baby #2. I have been away awhile and didn't know you had #2.
It DEFINITELY sounds like Silent Reflux. Abigail has silent reflux and I am an emergency room nurse and it took me 9 weeks to convince the doctors to take me (a nurse!) seriously. You need to be persistent. The weight gain means nothing. The only thing it means is that you are a good mother and persistent and conscientious about feeding him. The doctors tried to give me the same story but I just kept going back and changing doctors until someone took me seriously. Now (at almost 9 months), the Pediatric GI specialist has told me that Abigail has one of the worst cases of reflux he has seen. So obviously the general peds don't know much!
A really good website is
http://www.infantreflux.org it helped me tremendously when I was trying to arm myself with info for the docs.
Abigail was finally diagnosed at 9 weeks and continues on meds to this day for reflux. The doctor says she is nowhere near weaning off her meds yet. And she had all the same symptoms as your LO.
Sorry to hear you are struggling with it. You can PM me anytime with questions, complaints, rants, etc.
Good Luck at the doctor tomorrow!