I'm 17 and i believe i had recently had the flu about two weeks ago but some of my symptoms are still here, back pain, on and off chest pain, and neck?

Influenza: Flu symptoms can include body aches, headaches, fever and chills, dry cough, sore throat, extreme fatigue and malaise. There are tests that can confirm the flu that your doctor can perform. If you have ongoing symptoms beyond 2 weeks you should see your doctor for further evaluation to make sure it's not something else causing your problem.