My Baby Is 6 Weeks Old I Had Her On

my baby is 6 weeks old i had her on s26 gold from 2 weeks old. She started having reflux at about 3 weeks progressively getting worse. My doctor said to change milk to nan HA but since then there is no change and also now cramping and when wind is passed out her bottom she is in pain and screaming. Would gaviscon with the bottle help or should i change milk so isomil or infasoy?