Starting Slynd as an emergency contraceptive?

I started my period March 31st, not on any birth control. My cycles are typically 26-29 days (I’m 16 months postpartum, 4 months post weaning, so my periods are still adjusting). When I had my 6 week PP checkup, my doctor gave me a sample pack of Slynd, which has been sitting in my cupboard.

Well, my husband and I just had a failed pull out. I immediately went downstairs and took my first Slynd pill. Any chance it will do anything to prevent pregnancy?

Breakdown of the cycle:

Cycle day 1 - March 31st

Cycle day 5 - “Uh-oh” happened

Cycle day 12-15 - my typical estimated ovulation time, based on my previous 6 cycles

Am I in the major danger zone? Has anyone used Slynd like this before?

(ps - it would be ok if I were pregnant again, we want more children, it’s just sooner than I want.)