What Are Letrozferti, Fertigyn Injection And Duphaston Given For?

Hi, I am 37yrs old and trying to concieve. I am taking thyroxin since last 2 months as my doctor s prescription. I also took 5 tablets of Letrozferti from my second day and on the eleventh day was given an injection fertigyn-5000. On 16th day again the doctor told me to take duphaston 10mg for 15 days. Can anybody please tell me why i am being given so many medicines? My husband was also prescribed Paternia for a month (twice daily).