Feeling unhappy most of the time, sleep and appetite disturbances, irritability, feeling pessimistic and negative , poor concentration are indicative of a depressive illness especially if these symptoms have been there more than 2 weeks. Headaches and tremulous was could be because of anxiety which is often times comorbid with depression. It is treatable . Please visit a psychiatrist who will first do some tests to Make sure there isn't any other physics problem that is contributing to you feeling this way. Once that has been ruled out you can start medication and psychotherapy and make some lifestyle changes like exercise/ yoga/ meditation which will help you feel better.