OPK stay dark if pregnant?


I just found out that OPK can detect HCG! I started using OPK on CD17 and got a positive for ovulation on CD20 and CD21.

Currently I am breastfeeding and my period is returning to normal (24 days) but it can be a little unpredictable.

Do you think that a positive so late in my cycle could indicate that I am pregnant? The test line was very dark on CD20, but lighter today on CD22.

If I was pregnant would the test line remain dark?

What colour is the test line generally around ones period?