Anybody have any idea what this could mean?

•Jade•
So I'm on cd12 and I got my positive opk yesterday. ( I take three a day, morning afternoon and night) 
​This morning I took my opk, or so I thought, it was a preg test. Picked up the wrong packet. So I discarded it and took an opk. Showered and dressed ready for work, went back to opk to have a look and this is what I saw. 
So I thought just out of curiosity I would take another preg test when I got to work, thinking the first was a dud. 
This was the second one. Darker again. What the hell could it be. Only on cd12 and I defiantly had my AF
​Anyone experience similar thing?
​Thanks sorry about the long post. Freaking out! X