Help ! - when to go for bloodwork?

Hey all,

I need some help.

I usually get blazing positive opk's around day 19-20.

I got a dark-ish one on cd 18(not positive or peak though, test line was slightly still lighter than control line, as you can see below) and ever since then it has stayed pretty consistent in colour with it fluctuating a little bit lighter.

I didnt log cd 19 but that was negative as well.

I am supposed to go for bloodwork to see if I ovulated.

I'm not quite sure when I should go?

Should I keep testing to see if I get a positive. I'm on cd 22.

Any help would be so much appreciated :)