What Causes Sickness, Dizziness, Headaches With Loss Of Appetite And Dysphagia?

Hi, I feel sick,dizzy,have headaches and loss of appetite all the time. If I don't eat I know I would lose a lot of weight. Also I find it difficult to swallow. this has been going on for a year now. Sometimes these symptoms increase and I have fainted once. I would like to know more about it.