Why Is Duphaston Tablet Prescribed For?

hello and good day! I am a PCOS patient. I had may first day of period last July 18 not too heavy as the normal period. i was only used 1 napkin in 1 day because it s not that heavy as before or would i describe it as spotting. it lasts for 5days totally no stain on my underwear. I informed my OB abt it and she told me it might be my period because it was my day 25 that time. she instructed me also to take dusphaston on 30th of july. would it help me to get pregnant as far as i know dusphaston will be given to you if you have missed period but not pregnant. im confused pls help me make things clear.