Hi OP, poor you and poor lo with reflux. I've had 3, all with reflux so I can empathise.
I say 3 with reflux but please just bear in mind without a scope (camera) exam reflux can never be 100% confirmed. You and the medical professionals just have to go off your best estimate based on lots of symptoms. The other thing to bear in mind is that all babies have a touch of reflux as the little flap to the stomach is underdeveloped for a number of months, just some babies are much worse than others.
My first found gaviscon great relief. She was a different child after going on it around 12 weeks. Every moth or two we tried taking the gaviscon away to check it was still working and she immediately got worse until c10 months when it all resolved itself.
Second baby gaviscon was tried first and it didn't work, then we moved on to ranitidine, the losec and finally a pedeatrician recommended a formula milk called Enfamil. It thickens up when it hits the acid in the tummy. It was fab!!! She stayed on it til around a year.
Third baby settled on ranitidine and he only needed it until around 5 / 6 months.
It's all a bit of a testing game to wait and see what works.
Other signs can be if they are hoarse sounding, or sneeze a lot or get more distressed lying on their backs. Our pedeatrician recommended our ds to sleep on his front with a mattress monitor to check breathing (we used the Nanny brand and it was great) and he got huge relief from this.
Also try raising one end of the crib (stick a few books under) as the tilt can really help.
Hope all goes well for you with the gaviscon but if it doesn't work move on to try the next thing ASAP as the thing about reflux is its all trial and error so sooner you can find something that works happier you and baby will be!!