Query regarding digestive issues. Not?

My 4m old baby keeps on grunting for most of the day - more during the evening and night. Keeps waking at night. She stretches her hands and legs and makes continuous grunts. She is also prone to vomiting and and throws up from nose and mouth quite often. All of these are more during the evening to night. Mornings are better.. Upon talking to her pediatrician, he gave Neopeptine drops (5 drops twice daily for 5 days). He is also suspecting overfeeding. And has asked me to feed her every 4-hourly during the day and on demand at night. While I am okay with the meds ut I'm not sure about the feeding part, she pees more than 15 -18 times a day. Currently she feeds almost every hourly or at max once in 2 hours (only if I am not available) Kindly suggest...also how do I know that she is overfeeding or not? Ps - she is currently exclusively on direct breastfeed. She has lactose intolerance - was partially on low lactose formula till 1 month ago.