A dream about lactating is thought to be a represent the maternal instincts of the dreamer.
If you already have a child, this could symbolize your bond with them; if not, it could be interpreted as a manifestation of your desire to be a mother.
Allegedly, the more milk you produce in your dream, the more enthusiastic you are about the thought of having children.
Does This Mean I'm Ready To Have Children?
Not at all - just as picturing your dream wedding doesn't mean you're ready to get married. Dream interpretation is not a science and you shouldn't base any life decisions on it, so just take your time and don't rush into anything.
Has anyone close to you had a baby recently, or are you approaching a new stage in your life? Going to college or getting engaged can be big changes in your life - and the motherhood associated with lactation could be symbolizing this.