Lactating

I started lactating today and it freaked me out at first (FTM, I'm 16 weeks and 2 days). I thought it was just sweat at first because I was laying on my left side and my boob was pressed against my arm. When I moved I noticed a decent amount of clear liquid left on my arm. I look at my nipple and see it's soaked, and proceed to gently squeeze the other and notice liquid coming out. Has anyone else had this happen around 16 weeks?