When to test if very long cycles

[Faintlinesquints]

Hi, I'm not tracking ovulation but I'm wondering when I should test.
My cycles are usually around 6 weeks.
I tested just before Xmas and bfn, would that have been too early?
Tomorrow will be 7 weeks exactly since my lmp, the longest it's been for the past year.

When TTC my cycles were about 35 days long. I used to have 18 days between ovulation and the start of my next period.
Christmas eve wasn't too early, I'd test again in the next day or so.

As I recal for most people with a long cycle it’s always the same side of ovulation is extended so if you do basal temperature measurements and can work out when you ovulate that might help. What to Expect When You’re Expecting has good info.