Should I count my darkest OPK as positive?

Since I've had my LO 7 months ago I have only had two cycles due to exclusively breastfeeding. On average they have been 66 days long. My husband and I are currently TTC #2 and are using OPK's to track my LH spike. On the 15th (CD 38) I got a very dark OPK but not quite dark enough to be positive. I figured I was about to peak so I tested again 4 hours later. That OPK was still dark but a great deal lighter than the previous on. Ever since then the OPK's have been lighter and lighter. Could the darkest OPK have been my positive? Should I count myself as 6dpo? I'm so confused. Thoughts ladies? Below is a pic of the darkest test!