CBAOPK as pregnancy test???

Lauren
OK y'all, I'm so confused I am 3DPO,  i've been using the clear blue advanced digital ovulation test to help me find my window of when I ovulated and obviously that was recently. When I took this this morning I did it just for the hell of it and I got an empty circle, however when I took the test out and looked at them there is clearly still two lines on them the Control line and the test line, the test line isn't as dark as the control line but it is obviously very visible and still there so I was just curious what anyone's experience with this was and why I was still getting lines on them if that hormone was not my body anymore, then I heard that you can use the opk's as pregnancy test because they'll detect it so I'm curious and was wondering if that's what it's detecting except like a very very very low level of it, I'm not exactly sure I was just curious if anyone else has had this experience or something similar to it and what it meant. Thanks