Breastmilk

Hi, ftm here... and just wondering how do we increase our breastmilk. Anyone have any advice on that? My breastmilk has been decreasing since baby born. It went increase for just 2 days and decrease after. I've been eating confinement and lactation food, drinking plenty of water, and even latching baby to suck or pump. Checked with doctor and was given multivitamin to help with lactation. But, my breastmilk just seems to not increasing.