please can someone help? my baby was born 11 weeks early, now is doing well. she was on nutriprem2 which is a milk formula specially to help babies catch up. she started throwing up at each feed. took her to the doctors who prescribed gavisgon infant. but she still threw up. so i changed the milk. she was ok untill about 3 weeks ago when now she started gagging.. sometimes in the night which is scary. and in the day too. im not sure what to do. its scary when it happens. and i have to really pat her on the back tp help her. then shes ok. what is setting her off?