Thanks for the query to H.C.M. Forum.
According to your query you are not pregnant .
Since you mentioned that your husband has sex three day after menses , so no chance of any pregnancy.
Duphastone is dydrogesterone
hormone and usually prescribed for many diseases as in , Endometriosis
recurrent miscarriage, menstrual disorder
, threatened miscarriage
, endometrial protection during menopausal hormonal replacement therapy.
As your query is "can you take duphastone continue?
Since you have not mentioned in query indication for duphastone .
The best way is to consult your Gynecologist and get his opinion.