Implantation or Af?

Nicole • 28yrs old & TTC #2
How do you tell the difference? Im due for AF in 3-4 days but when I wiped this morning I had what looked like EWCM with little blood bits in it.. Ive had no cramping, vomitted yesterday and getting BFN. Is it too late for implantation and its just AF showing her ugly head early? Opinions please 😊