Gynic problem. Delay in menstruation.

In 2014 we got married and born one kid.later again got conceived in 2018 March and got miscarriage in 2018 June. In 2020 again we visited the doctor she did all the tests and said PCOD and also did the follicular study for three months .And said the dates for sex, we did the sex even though she was unable to conceive.my sperm count was 66 million/ml. And motility was 80%. During follicular study doctor given HCG injection ,when HCG injection given next month menstruation has been delayed. Even after marriage she is conceived for first month it self .now even though my wife going under treatment for past two years no result.why?is there any further investigations. No thyroid.and lmp was 9th December and did follicular study and said egg released on 23rd of december.and tested for pregnancy on Jan 13 BFN.And again she got menstruation on January 20.actually egg released on Dec 23rd and menstruation due was Jan 10th .why delay In menstruation.