Hello & thank you for posting on HCM Duphaston is synthetic derivation of naturally occuring hormone (progeterone) - which is predominantly secreted by ovaries to help maintain & thicken linng of uterus to support implantation & subsequent pregnancy. As your last period was 2nd april & you had taken tablets from 17th to 26th (i.e D15 to D24 of cycle) - it was correct regime, if implantation had not happened - within 2-3 days of stopping duphaston you would normally start periods if you are not pregnant. But if implantation & subsequent pregnancy has happened - periods will not come after stopping duphaston (interval of 2-4 days) & in that caes I suggest you must take home preg test first. There is another possibility where stopping duphaston may not start periods ( this is normally due to lack of estrogen in the first of half of cycle) but to diagnose this one needs to have progesterone challenge for 1-2 cycles & also USS for ovarian tracking. Hope this is helpful