Aptamil Peptide 1

Looking for some advice! I’m certain my son has silent reflux and got told by the health visitor and midwife he does (all the symptoms) tried gaviscon from the doctor but made him constipated. Went to the doctors again and they’re trialling him on Aptamil Peptide 1 but we’ve had our worst day/night with him. He’s been agitated, crying on the bottle, spitting up & being more sick than usual like a clear liquid (it seems the texture is much watery so easier to spit up, which doesn’t make sense when he clearly has reflux?) and so stuck on what to do next??