faint line after bfp

Daniela

hey ladies!! little help here please 🥹 so i tested on december 6th and for 2 days after, the lines were super dark and obvious! i got an transvaginal ultrasound cause i went to the er and dr said she could see pregnancy forming (i have next appt dec 28th) but i just tested right now out of curiosity and the lines are very faint… what could this mean?