Today it 14 days since my previous period i'm seeing brown discharge. what could be ?

Many possibilities: Generally this represents discharge of old blood from the uterus. The reasons for this happening are multiple, but generally not representative of any serious problems. As long as you don't develop other symptoms this should resolve uneventfully. If it recurs frequently you might, at some point, want to be examined by your gynecologist, but for now would relax and go about your life enjoyably.