Hi Please check if the sleep disturbance is real due to lack of feed..Yes formula feed addition is always ok if mothers milk is Insfficient..Insufficient mothers milk is known from the weight gain of the babu and no of times the baby pees after every feed or not...And to increase mothers milk production mother to drinka atleast 3 liters of water..eat protein rich food and fryita veggies and GLV ..If not its always better to give formula rather than making kid dehydrated along with breats milk

Consult to Pediatrician physically for further evaluation and treatment

Yes if mother feed is not sufficient and baby is still hungry for feeed then you can give formula feed on and off