Possible Implantation Bleeding or Early Period?

I chart my temps/cm and confirmed ovulation on July 21st (CD 20). I am currently 15dpo today. Period was due yesterday or today and the latest. My luteal phase is 14-15 days.

I had a dip in temps 6dpo-7dpo then it shot back up .9 degrees 8dpo. I started spotting-light bleeding 6dpo-9dpo. The bleeding never got more than like a light period day. It was dark red to brownish blood, never bright red. I took a test 12dpo (2-3 days before my period date) and it was negative. My periods are usually light to medium.

What are the chances that last week could have been implantation bleeding or just a super early period? Sorry for rambling and thanks in advance for any insights!