I've been having unprotected sex for about 3 weeks now. My period isn't very regular but was suppose to come Jan 21 but it didn't. I took a pregnancy test 2 weeks after I had unprotected sex but it was negative now I have had a brown discharge for about 3 days that isn't heavy like a period but isn't spotting either. Today is the 3rd day of having it and it's starting to slow down and I've had no cramps. Is this implantation or my period beginning to start?