my periods had always been ontime or two days earlier all these years.now i am 36 years old.since last two years approximately,it is usually 4-6 days earlier,and it is just scanty black spottings on the first and second day,and the really red discharge starts on the 4th day only.it is really heavy just for that day.finishes with black or dark brown discharges again until 7th day.i'm trying to conceive this last two years and i'm finding it difficult to calculate my first day of period inorder to calculate my ovulation.i doubt if i seriously ovulate?all this worry me so much.i am already on prenatal vitamins and follicum.i had been prescribed duphaston and glucophage as well.nothing seems to work.kindly help.need your expert advice.wanting to become pregnent very badly.i'm already a mother of two girls,12 and 7 respectively.what could be wrong,or what should i do,please suggest.