What Causes Milk Discharge From Breast?

mam, i am 21, today i suddenly noticed that my breast was slightly milking.To check when i pressed them i saw 1-2 drops of milk coming out.i m deeply worried, is anything serious or can be fine in some time? is this a symptom of cancer, tumor or anything normal like stress? i had very stressfull days in the past weeks.please suggest soon.