Nipple discharge?

Elizabeth

So I took a pregnancy test the other day and it was negative. My periods are irregular so I don't know when my next is due, but I do know that my last period was over a month ago. This morning I noticed a milky discharge from my left nipple. I squeezed and more came out. I have no idea what this means?

Out of one duct comes a milky discharge and out of another a dark green. I read that both are normal colors. Never had this before..