Baby doing vomit after breastfeeding.

My baby, 1.5 months usually feeds milk every 1.5 hrs to 2 hrs and I feed on demand. But he is having reflux and his tongue is coated with white milk, he vomits thrice in a day and doesn't do potty everyday, usually does after 6-7 days. Doctor had prescribed him Colic aid as he cries a lot in the evening due to colic. We gave him twice last week, he passed stools. But I don't want to give him more of it as he may become used to it. Is it ok to feed on demand or these problems can be avoided if I set time and feed him? I am also unable to set time for his feed as he cries every 1.5 to 2 hrs and doesn't stop till I offer milk. No matter what we do, he wants it. One doctor says, let him cry and don't feed him till there is a gap of 3 hrs, another says feed on demand. I am so confused, please help.