feeding problem

my son is 12 weeks old and about 6 weeks ago the health visitor and 2 doctors believe he has reflux. he doesnt throw his feeds up but kept screaming on the bottle as if in pain. i tried collic drops at first and no improvement but then was told to try gaviscon. this worked for about a week and a half but then hes started screaming again. ive had him checked over by the doctors numerous of times and he is always fit and well. i told them gaviscon doesnt work anymore so hes now been put on ranitidine and domperidone and its been a week now and no improvement, now he plays with the bottle loads! he bites it and just lets it roll round his mouth and screams everytime you put him in the feeding position. the health visitor fed him today and its like she said, he seems to know theres going to be pain which is why hes getting worse as hes associating the bottle with pain. he does drink eventually but it takes over an hour for each feed. ive changed teats an bottles aswell and no improvement either. by monday if the teats dont work still and neither does the paracetamol they said they will change his milk. does anyone have any other ideas as to what it could be? because everyone i no is stumped and im at my wits end with it all. thankyou