What Causes Chronic Nausea,cramps And Lethargy?

I am a 21 year old female, i'm 5 feet tall 100 pounds i eat very healthy i excersize. I have been sick for years doctors do not know what is wrong.Ive had an endoscopy and colonoscopy and they find nothing. I have dizzyness, naussea, stomach pains, vommiting on occasion, constant headaches, chronic fatigue and tiredness, cold hands and feet, light headed, thinning hair on hairline, body pains