What Causes Longer Periods, Fatigue, Headaches And Neck Pain?

Hello...I am a 17 year old female and I have very painful headaches...as well as neck pain and upper back...I have recently become very tired...constant fatigue and have lost a bit of my appetite...I have lost a bit of weitgh due to this...and my most recent period was much longer than it usually is...it usually lasts three days but lasted an entire eight days....do you know what's wrong with me?