Brown spotting 5 days in a row

Katherine • We have been actively trying since July 2015.
I had my first IUI last Monday. I experienced some light brown spotting which went away after a day.
But I am having spotting/discharge starting 4dpiui until 8dpiui (today). Is this normal? AF is not due for another 6 days.
I'm thinking this can't be implantation bleeding since it's too early and it's been going on for 5 days now. This has never happened to me, ever.
Did anyone experience this after IUI but got a BFP?