Implantation bleeding or something else? (No pic)

Tania
I had two days of brown spotting, at 9 and 10 DPO. (Today is 11 DPO so not sure yet if it's continuing.) I don't want to get my hopes up, so please tell me what this could be OTHER than implantation bleeding. I don't usually spot this soon before AF 
​I did take Wondfo HPTs both days of spotting - both neg. Waiting until tomorrow to use a FRER.