Two day period or something else?

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? Tested cd26 and today cd30 with fmu and both neg. Any possibility I'm still preggers? I had lots of symptoms leading up to the 28th- bad acne, oily skin, headaches and fatigue. Thanks for all the advice!