late period/discharge

What do you guys think is happening?? I am 3 days late.... I have been nauseous, getting headaches, sore boobs. Slight cramps. I never get nauseous before period. My husband and I are ttc for 3 months...had a mc last month....AF still has not arrived but when I went to bathroom I wiped and a VERY light brown discharge. Is this the start to AF or could this be implantation? Not sure. Took a test bfn....