My blood tests are normal but II am tired, I just had ultrasound on thyroid too and normal but only slightly enlarged, so what is going on?

Many causes. There are many causes for fatigue, thyroid issues are but one. See your family physician to determine the etiology. Other things to consider are sleep apnea, insomnia, vitamin deficiency, poor diet, poor exercise, anemia, cardiopulmonary disease, depression and many others.
Fatigue. Do you sleep well? Do you work swing shift or night shift? Have there been major stressors in your life recently like new home, marriage, divorce, new job, job loss, loss of a loved one or favorite pet? Perhaps your doc should screen you for depression. Congratulations that blood work & thyroid us were normal.
Fatigue. Many people experience fatigue for a great variety of reasons. It is possible that it is due to some metabolic condition that has not been checked, or perhaps some other problem. Regular exercise, eating small healthy meals, and taking a multivitamin daily should help.