Hey MummaB

The pain is horrible to see isn't it..I really sympathise with you.

The doctors may try another drug called Zoton. It falls into the same type of category of Losec, and again decreases the amount of acid the stomach makes. Our paed said that was an option for us, but we used Losec. But you know what, I still wouldn't lose out hope yet that the losec won't work.
If I was in your situation, I would definitely be trying some thickener with the bfs (like guarcol) as that would help keep the feeds in his belly, and therefor in time and in conjunction with meds, should reduce some of the pain he is feeling when the stomach acid creeps up. And of course positioning upright.
I guess if all that didn't help, there would be good reason for the specialist to organise some more tests to see exactly what is going on, and to confirm that it is reflux causing the pain.

Anyway, this is probably not much help but just thought I share it anyway.
Once again, hang in there.