Near back pain. Out with this situation.

Hi , am akshita age 26 years married recently . I have severe back pain from.past 3weeks , I have regular periods , normal stools . The pain is like dat am in my periods but am not . I don't have any fever cold and also am tested negative for covid .last month I have taken multivitamin tablets and dolo 650 mg also am vaccinated . After vaccination I got full fever and body pains which are there at present also nd took dolo650 . But still I have back pain very severe past 3days am not taking any tablets . I usually get fever every month around 100 at dat time I take paracetamol and it will gives me relief from dat . Kindly suggest Wats the issue for me also if required tests pls prescribe me . Kindly help me out with this situation . Thanks, Akshita .