Wth?!?!

Okay so im pretty sure im about 7 dpo. I started spotting yesterday. It got a little heavier today and is already starting to stop?! I got positive opks 3 days in a row before this bleeding started bc i thought i didnt ovulate yet so i continued testing and now this? Is this implantation bleeding?! Usually by now i have a way heavier flow and its just stopping?? Oh and i was still 9 days away from AF when this started yesterday..... it looks different than AF too (usually its bright red and a lot and right now its super dark and barely anything) CD 21 today.