When do your lines start getting darker???

This is my first month testing. I have a shorter cycle, 24 days. So, my app said I should've ovulated yesterday, but I'm coming up so faint. Then, today not even a faint line! I'm thinking I just probably didn't ovulate this month. This is the first month i had a truly regular cycle since my ectopic in March. We were so excited to start testing and trying, and now we're feeling discouraged again. CD6 was actually the darkest line. They started to fade each day. My periods last for 3-4 days. So, perhaps I ovulate like right after and missed it?

Should I keep testing everyday, or cut back to everyother day? Won't my lines gradually get darker and darker? Any advice would be helpful! Thanks!

UPDATE: Here's my bbt, no fluctuation really. So, I really don't think I've missed ovulation.