Please help and answer to this. Have?

Hi Doctor, My daughter is 35 days old she weighs around 3.6kgs. Earlier she use to drink milk and sleep well and also not often cry. But from last 20-22 days after drinking milk she starts crying and after a burb and spitting out some milk she feels better and sleeps. But this crying and spitting of milk process takes good 25-30 mins. She cries alot. I'm very concerned. Is this normal or is there any problem with the baby? She was fine before this 20-22 days. We had consulted few pediatrician's near home they said it's cold and because of it, it's taking time to digest and it would be fine and recommend a nose drops. We are giving grape water and everything. But the issue is still there. We are feeding her with both mother's milk and formula. In both the milk type she is comfortable. Plz suggest if anything needs to be done or what actually the problem the baby may have? We are having sleepless nights because of this plz help!