Getting close? Confused..

First month charting! ... OPKs seem to get darker, then lighter, then darker - opposed to slowly getting darker each day.

Bottom opk was taken today (CD 15). This is the darkest it has been, so far, and showed up almost immediately. I think all the others have dried a little darker than they looked at 5-10 min.

Is the one from today positive? Or getting close?

What would be the best time to BD? bbt hasn't really spiked yet, so I'm not really sure what that means in relation to OPKs...