Spotting question **progesterone supps**

Laura • Expecting #2. 2mc feb 2015 & July 2015 👼👼 Lyla born 11/5/16💗
Hi ladies! I have been on progesterone since 4dpo and today at 14dpo stopped as all tests show BFN. I had some light pink spotting that I thought was the start of my period but then nothing! I am 1 day late with AF, anyone have any idea what this could be? Related to the progesterone??