Last cycle was 41 days when should I start checking OPKs this cycle?

Chloe

Last cycle was 41 days long. My period was actually due on the 22nd Feb but it only arrived today at 8 days late. I had spotting on 3 days leading up to my period starting, 26th, 27th, 1st. It started today (2nd March)

When should I start testing with OPKs so I don’t miss my ovulation window?

My cycles have been messed up since my miscarriage last year.