I have lost interest in sex and i feel i can do without it. how can i get back the interest

Great question: The most common cause is depression at your age. However fatigue from diseases or lack of sleep can affect your sex drive as well. Your relationship with your partner is yet another important factor. Consult your doctor to check on your health status to be following by psychologic counselling if indicated.

Great question: If you're in a relationship, this is very serious. When this happens to a youngish man, and includes loss of interest in his favorite pictures / ideas and loss of morning erections, it's often due to a prolactinoma or hemochromatosis even if testosterone is normal. In a woman, it's trickier and there are things nobody understands. A good physical exam & discussion is a good place to start.