Frequent Fever, Headaches, Bad Throat And Sinus. Negative On Strep And STD. Suggestions ?

Hello doctor, I have been struggling to find out what is wrong with my body the past year and a half. I ve been getting sick mostly fever, headaches , throat really bad, and sinus . I ve gone to the doctors severall times it was getting so out of hand that i dont want to go anymore because they will say nothing is wrong with me. I cant figure it out. I ve been tested for strep mono and all the STD s. And nothing came up. The past week I ve been having abdominal pains and they won t go away. I dont know what to do anymore. Any suggestion will be greatly apprecaited. Thank you