Can Plan B fail after light spotting?

My cycles are a bit shorter, because I'm still breastfeeding our toddler, but I have conceived and had a chemical pregnancy twice previously while breastfeeding.

Last menstrual cycle was 13 January through 19 January.

Unprotected sex on 24 January, took Plan B on 25 January.

Peak ovulation test on 27 January (so ovulation I assume around 28 January).

I've been spotting very lightly on and off since 30 January through today (3 February). When I say light, I mean light - pink and watery, and only notice it when I wipe - nothing on a pad or liner at all.

I know I've read Plan B can cause spotting simply because of the hormonal changes, but that you aren't in the clear until you get a period (which could come a week early or a week later).

Has anybody had spotting after taking Plan B, and still ended up pregnant? I don't even know how I feel right now. Somewhat relieved hoping it works, and disappointed and guilty for taking Plan B at all. (Please no judgments, lots of emotions.)