Hello dear
Understand your concern
Following are the causes of light vaginal spotting in your case.
Withdraw bleeding due to stop taking
duphaston, subchorionic bleeding (bleeding from fetus),
missed abortion and ectopic
pregnancy.
You have to consult the gynecologist and go for vaginal examination and USG scan to diagnose above cause.
Missed abortion and ectopic pregnancy should be treated by surgery.
If USG will come negative then most common cause is withdraw bleeding due to stop intake of duphston.
You have to go for blood
Progesterone and HCG level measurement.
If still found low, Duphaston should be started at 19th week of pregnancy to maintain the pregnancy and it does not affect the fetus.
Susten vaginally tablet should be taken as it is more effective.
HCG injection should be given if found low.
Do compete bed rest for few days and avoid exertion as it aggravate the spotting.
Hope this may help you
Best regards
Dr. Sagar