Family Planning : Depo

Hi mga momsh, i got my depo shot nung Aug.21 for 3mos po it will last Nov.21. Last contact namin ni hubby is november 10. Then Nov.21 nagkaregla ako pero di sya yung normal na madami panty liner lang ang napupuno 1week pong ganun..kaso until now wala pa din po akong regla. Im just so worried, maari bang buntis ako o sadjang bumalik pagiging irreg ko? Please help me. This is my first time na mag depo and i dont know kung anong nanyayare after maglast yung 3mos.na depo. Thankyou ??