Please, help!

Eff • ♡ttc since September 2014♡
I had my first <a href="https://glowing.com/glow-fertility-program">iui</a> sept 18... AF is due on the 4th, but I started spotting pink/ brownish discharge last night and today. Which is very unusual for me. Every pregnancy test I've taken is negative... advice.. suggestions on what this means. Should I call my dr?:/