Spotting? Why?

I though I ovulated on cycle day 19 or 23 but temps are keeping low. I am on my third month of vitex and cycles have been getting shorter. So I have no idea why I had spotting and slight cramps (tugging) on left side. Can't be ovulation cause there is no CM and timing is way off... Can't be implantation cause temps are low. Any thoughts? Very frustrated:( AF not expected until after aug. 12th but who knows.​