Check for a dairy intolerance! With my first it took 1 year of being told it’s reflux by the docs when actually he had a really bad soya and dairy intolerance. He was being sick all the time, unable to settle him and losing weight. So definitely look in to it if the likes of gaviscon etc aren’t working. X
Contact the health visitor they might be able to help. If it is really bad it might be a dairy allergy but again they’ll be able to see the signs and tell you about it