Implantation Bleeding??

The glow app says I am supposed to start my period on Tuesday the 21st based on when I ovulated. Before I updated my ovulation earlier this month, I was supposed to start my period on Friday or Saturday (17th or 18th). I just went to the rest room at work and when I wiped there was a little pink mixed in. I only checked the toilet paper because I say pink droplets in the toilet. Glow originally had my estimated to ovulate on the 3rd of the month but after taking OPKs (Clearblue), I got the flashing smiling face on January 7th. Do you think this is the start of my period or possibly implantation bleeding? Should I test—I’m only 9DPO if calculations are correct. Thanks yalll!