My five month old started fussing at the bottle...

My five month old started fussing at the bottle about a month ago, he went from generally having his quota (roughly 180mls) every four hours to dropping 20-30mls occasionally. I wasnt too concerned as I know a baby will eat when they are hungry. In the last three weeks this problem has progressively gotten worse, by worse I mean he was only having on average about 80mls per feed every four hours. I took him to the Dr's and because he wasnt dehydrated or showing any major signs of illness the doctor passed it off and told me to see the Child health nurse about it as he didnt know why he was doing it but no cause for a Paediatrician at this point. So I tearily trudged home and tryed a different formula and different teats, no luck. Now in the past two days he has dropped to 40mls per feed. The Child health nurse came to see us, weighed him in at almost 1kg less than 9 days before and viewed him feeding and wants him referred to a Paediatrician ASAP, she was very kind but said it was an unusual case and had no answers and that it was something not to be ignored and to watch for dehydration signs. He is being assessed by the speech pathologist next week to make sure there is nothing mechanical about the problem i.e. tongue tie or problems with suck/swallow reflex. He is being treated for reflux with medication also. So ladies (and gentlemen), I sit here very worried about my little man, nobody has any answers yet and I am stressed he will end up in hospital by the end of the weekend if he dosnt pick up. If any of you have experienced this hunger strike to this extreme or have heard of anyone else please let me know your thoughts as I feel very helpless and lost for answers. Thanking you in advance - Katie