Spotting

Last month and this month I've spotted verryyyy light only when I wipe for like one or two days. Anyone know what that could be?

Always had irregular periods I have a 1 year old daughter and had a miscarriage 2 months ago.

I took a opk to rule out ovulation and it came back negative?

Spotting doesn't bother me im just curious. Yes I've been to drs and they don't know either..

Anyone else spot for 1 or 2 days once a month? Haven't had a full on proper period since the MC either.