Help! Dark lines

I’ve been off BC for 11 weeks, started testing OPKs 5 weeks ago, finally got a positive test yesterday around 3pm, tested again 4 hours later and it was lighter so I thought my surge passed. Tested again this morning and got an EVEN DARKER line! What does this mean? I know you’re not supposed to keep testing after your first positive but whatever. What day should I count as Ovulation day, Today or tomorrow?

(I had nausea and a light migraine yesterday, and kinda crampy this morning with a dull headache.)