duphaston is a progesterone
which will help in implantation
of gestational sac
after fertilization, as implantation occurs around 2 to 3 days after fertilization you can take duphaston on 16th day,
just by taking duphaston the chances of fertility won't improve usually,
you first track your ovulation by natural methods or by ovulation kit or by ultrasound
then plan intercourse around that time, be sure that the seminal parameters of your husband are normal,
then there is possibility for fertilization.
if any of the above parameters are defective then you or your husband have to go for medical treatment to correct them.