Nutramigen Reflux

My 6 week old baby girl has been on Nutramigen for around 3 weeks now for suspected CMPA. Her allergy symptoms seem to have improved quite a lot, but she’s still seems to be in some discomfort with her stomach with diarrhoea (although nowhere near as bad) and a lot more reflux since swapping over. I think the reflux is the main issue. Doctor gave me some Gavsicon infant for her, but warned it could cause constipation. Has anyone had any similar experiences? Did the Gaviscon help?