been spotting brown for the last 12 hours.. :/

Danielle
This is totally out the norm for me.. I've never actually had ovulation spotting or not that I've ever noticed anyway for the last 12 hours I've had brown when I wipe.. totally unusual for me, me and hubby promised we would just let nature take its course this month.. and not obsess over every little thing so I've not been tracking...
But it's hard for me not to when odd things like this arise,,, I had a few opks left in the Cupboard from a few months back and with me spotting I just wondered what you all think to this OPK? I took one last night and it was slightly lighter than today's.. 
I never usually OPK in mornings when I have in past but I just needed to for my own sanity.. is there a possibility I've ovulated and my surge is now dropping and this brown scanty bleed is the result in my mid cycle bleed..? Glow estimated my fertile week from Saturday-today with yesterday being my peak.. possibility I've just experienced ovulation break through bleeding!???