My baby is a month old. He has milk allergies, lactose and tolerant, also he has acid reflux. He is…

My baby is a month old. He has milk allergies, lactose and tolerant, also he has acid reflux. He is currently on gas drops and acid reflux meds. Before we found out he was lactose he always strained very hard and cry when he try to use it. Now that the doctor changed him to Soy formula, he still strains and cries when he uses it. He isn't constipated, his bowel movement isn't hard. Does anyone have any insight? It hurts seeing him strain and cry just to use it.