Hello Doctor. My Age Is 24 And I Have Also

Hello doctor. My age is 24 and i have also 1 year baby. My period is regullar after pregnancy but now my period is not regular about 2 months it came late and this month my date is 31 and its not coming now.. I checked pregnancy test but its negative. I am very worried why is my period not coming. But i take also regulin forte medicine bt its not working at all now. Plz tell me what should i do??