That is an excellent question and one that is best answered by your primary care doctor
or other medical care provider as he or she will best be able to evaluate your medical history, physical examination and any associated comorbidities to elucidate the cause of these symptoms. It is very difficult to elucidate the cause of your symptoms from the limited history provided, but here are some common causes of the symptoms you are describing. One of the most common causes of fatigue, mood changes, and possibly even the headaches is depression
. There are several other associated conditions such as lack of appetite, lack of enjoyment of things that used to give you joy, and difficulty sleeping. If you have these symptoms, your doctor may choose to put you on a medication to help you with the depression. Oftentimes, this can be very helpful to people with depression. Other causes of these symptoms include pregnancy (it is unclear if you are a male or female from your history), thyroid dysfunction, abnormalities in blood levels of various vitamins and minerals, and dehydration. Your doctor can perform tests to find out the cause of your symptoms and can then decide upon the right course to treat you.