Is The Light Brown Spotting I M Experiencing A Possible Side Effect Of Duphaston After My Missed Period?

Hi, I missed my period on Dec. 9, and had light bleeding on Dec. 13 which is not my usual period which becomes heavy the next day. I took a pregnancy test with a positive faint line. Doctor advised me to take Duphaston, but on Dec. 21, doctor didn t see a gestational sac and fetus on ultrasound. I stopped taking Duphaston that day as well. On Dec. 24 I experienced a very light brown spotting until now, Dec. 26, still very light like it s literally just a spot. May I know if this is a side effect of the medicine. Hope to get your advice. Thanks in advance.