No af for October, spotting on 31st, help

So my last period was September 8th, I did not confirm ovulation for the month of September, did not have a period for October, confirmed ovulation with OPKs on October 26th/27th (got a positive on OPK at 3pm on October 27th and by 9pm it was gone, barely was a line), had some spotting on October 31st at 11am, put a tampon in and at 2pm I felt uncomfortable, so I took the tampon out and noticed nothing was on the tampon. Around 3pm I had sex with my hubby cause I wanted it so bad (which I usually do this right after period).

Do you think that I missed my period for October and didn’t ovulate in September? Could I have had implantation bleeding on the 31st?

I might add that I took a pregnancy test just now 11:45pm

Bfn!