Lactation at 20 weeks?!

I literally just hit 20 weeks today. Laid down for bed and was asleep maybe an hour and a half. Woke up cuz I had to pee and my shirt was SOAKED. I pulled my shirt up in the bathroom and I have full blow started lactating! Scared the heck out of me! Is it normal to be lactating already? How about large amounts? HELP!!!