15dpo shouldn't it be darker?

It's not an evap, it showed within the time limit. And there is no indent. I just would expect it to be darker by now... I'm one day late(ovulation determined by BBT and OPK) I'm worried that my progesterone levels aren't high enough and my little miracle isn't growing :( idk what to do. My doctors appointment isn't until the second and I fear it'll be to late.