milk is suddenly disappearing?

i am a little over 4 weeks pp and am exclusively breast feeding. up until today i had enough of a supply to satisfy him off of one side . now today i can't even pump out half an ounce and he seems to be continuously hungry not in a growth spurt way more like he isn't getting anything. he nurses and ten mins later tries again and still doesn't seem to get anything. what could be causing this sudden decrease in supply?

Up your fluid intake, and start taking fenugreek 3 pills 3x a day

Are you feeling a let-down? Is your baby having lots of wet diapers?

Here is a great resource: http://kellymom.com/bf/got-milk/supply-worries/low-supply/

Also, babies nurse for reasons other then hunger. Your baby just may need some extra comfort right now (perhaps fighting off a cold?).

He has wet and usually dirty after every feeding. I drink about a 100 ounces of water a day. I did just come off of Reglan 3x a day.