I could tell when my milk dried up when I couldn't see it around his mouth anymore when he popped off. I could also express milk out of my nipple with my hand before it dried up too. Plus it hurt pretty bad when he was nursing dry. I was pregnant though, just didn't know your milk dried up when your pregnant until it happened and I questioned it on this site. Lots of good info. Are you pregnant, or is your D not nursing so much at all anymore? Is there any reason you would dry up?