4 days late and brown spotting?

Okay, I am 4 days late now almost 5 officially. And I have been getting bfns this week (latest was today.) I am never late but today I got about a teaspoon of brown discharge and I put a tampon in and I just checked it and nothing. Can implantation be after your missed period? I'm not sure when I ovulate(I don't test). Btw I don't have any cramps just nausea and a high cervix