2 day period or something else?

Cate
Hi everyone! Since I've been off bc I've had progressively shorter periods from 34 days to 32 and now I was thinking this month 30. I ovulated on cd16. However, I got some bleeding on CD28/12dpo that seemed like a period then on the 29th heavy in the morning, light throughout the day and nothing that night. Could this be my period or something else? AF usually lasts 4 days. Tested cd26 and today cd30 with fmu and both neg. I had lots of symptoms leading up to the 28th which were different from usual AF- bad acne, oily skin, headaches and fatigue. Should I keep testing? Be worried or just suspect it was AF coming earlier than I thought? Thanks for all the advice!