Gynaecology - missed period. Solution!

Last year I got married, April month conceived normally and June month miscarriage my first babby in 3rd month starting that time only dr diagnosed hypothyroidism for me and i take thyroid medicine and my tsh level below 2 , after three month again i try baby and i got missed period but negative pregnancy test, i went dr ofc my dr given dupaston tablet and i get heavy bleeding , next 3 periods are coming normally again i try to plan baby last month , i had heavy bloating stomach, fatique , constipation, gas,missed period but negative pregnancy at 35 th day, when i am intercourse with my partner that month i missed my period and negative test otherwise I get normal period kindly i want to know the reason and what happening in my body, and what treatment is better to recover my problem. Kindly given me the best solution