Breast Milk Supply Low??

My baby is 3 weeks old and ive been breastfeeding since birth and he latching on lovely. As well as pumping often when needed. Well recently meaning yesterday lol i notice i havent been leaking milk.. Normally i am always a leaking person i leak every minute.. Now i havent been leaking and when its time to feed my son theres nothing really coming out. What can i do to make my milk come out like how it was?? My appetite is ok but not perfect and ive also been kind of stressed.. But im in love with water i drink water literally all day.. Any advice ladies??