Implantation or AF? 2 days until period is due

Had sex 11 days ago (according to this app it was the last day of my ovulation period)

& starting last night I’ve had this discharge. Woke up and now there’s less and it’s more light brown now. I took a pregnancy test today and it was negative. According to glow I’m due for my period in 2 days. Any idea if this is AF slowly coming on or implantation? Is it too soon to test?