Hello I am 21 years old female. Since 3 days ago my vagina has been hurting and it seems red and it hurts a lot when I go pee. Also I have been having fevers, sore throat, back pains and headaches. What can I have? I haven't had sex for over 3 weeks and I

Infection somewhere. It sounds like you may have an infection. This could be a bladder infection or an infection in the uterus or elsewhere. You really need to see a doctor and get checked out to find out what it is because if you don't, it could get a lot worse. Best wishes!