breastfeeding moms..please help !

Jessica
I'm a first time mom and currently breastfeeding. I wanted to know what are the signs that your milk is drying up? My baby was born on Jan 14 and I've been breastfeeding since but I've been favoring my left boob over my right because it's the boob that puts my baby to sleep. Now that I'm trying to get both boobs to produce the same amount of milk, I noticed dry crusty milk on my nipple shield when I have baby feed on my right boob. Is this a sign? What can I do to get it to start again? I don't want to left with only one boob working. Anything helps! Thanks