Faint line

Took an opk April 30 in the PM (positive) and may 1 about 3 PM (also positive). Grew a wild hair and took one a few minutes ago just out of curiosity... There is clearly two lines, the test line being a lot lighter than the control but it's obviously still there. Now in the past when I have taken the opk there is no trace of a second line. What does this mean?? Any opinion is appreciated