Yeah i have had that happen to me too. Im 16 weeks and i think maybe for the past 2 weeks it happeens off and on. I asked my midwife and its nothing to be concerned about.
I read in yahoo health page- about nonspontaneous nipple discharge- it seems to be quite common, & not of any concern. Thank God, I was worried.
It is totally normal. it can happen at different times for women. You wont produce milk for a day or 2 after birth.
You should call the doctor.Some people start leaking earlier,but I thought it is usually later in the second trimester.