opk help please ?

I'm on cd 12 I usually ovulate cd 12 but my lines are getting lighter ? I had a darker opk cd 8 at 4 pm but they seem to have lightened since ... have I had my surge ? doesn't look as good as last month's ? first cycle since misscarriage ... I did do a pregnancy test which had a hint of a line I'm beginning to think I may of gotten pregnant before my period but it was a chemical bleeding did last longer than normal ?