pregnant or missed?

Rebecca
Hi ladies, 
I am so confused right now. My last period was 01/08/16 and i ovulated 12/08/16 and my period was due 29/08/16 however i accidentally done a ovulation test yesterday (picked up and ovulation tests rather than pregnancy) and it was positive 🤔 i have one billion percent already ovulated. I have just read as well that an opk can detect HCG so i could actually be pregnant but my pregnancy test is negative 😒😭. Some advice would be great please.
Every period i have runs like clock work.