Hi, your story sounds very similar to mine. Apologies in advance for the length of this posting....but hope it helps!
I too was brushed off weekly by HV and GP when I reported v similar symptoms to your 5 month old, the suggestion being that I had PND . Eventually I couldn't bear the screaming and protracted feeding sessions any more( sometimes it took an hour for her to take 3 oz) and took her straight to A & E who diagnosed silent reflux and provided her with ranitidine and domperidone. The Consultant confirmed that babies with this condition feed to soothe the pain in their throats that has been caused by the acid and that they don't always lose weight with it.
The lovely people here helped me out a lot, and on my posting gave me this list which may help you to identify if it is reflux and this link to a fab site infant reflux disease Good luck!
Gastroesophageal Reflux Disease (GERD) in infants
SYMPTOMS:
Baby may have all or some combination of the following:
pain, irritability, constant or sudden crying, "colic"
frequent spitting-up or vomiting (large amounts or small amounts ? or ?silent reflux,? where baby does not spit up at all)
vomiting or spitting-up more than one hour after eating
not outgrowing the spitting-up stage
poor sleep habits, frequent waking
pain while lying flat
"wet burp" or "wet hiccup" sounds
recurrent, painful or persistent hiccoughs
chronic dry cough
gassiness: from gulping air while crying and eating too voraciously
apnea ? voluntarily holding breath while eating or sleeping, air then comes rushing in with an audible wheeze (and if eating, choking and gagging following apnea)
constant eating and drinking (swallowing temporarily relieves the pain)
refusing to feed, arching back, crying on breast or bottle even though hungry
poor weight gain; weight loss; failure to thrive in extreme cases
swallowing problems, gagging, choking
hoarse voice
frequent red, sore throat
ear infections
constantly running nose; sinus infections
bad breath, tooth enamel erosion
excessive salvation, drooling
peculiar neck arching, Sandifer's Syndrome
respiratory problems; pneumonia, bronchitis, wheezing, asthma, nighttime cough, apnea, aspiration, noisy or labored breathing (extreme cases)