Hello laeeqchughtai Welcome to HCM Erectile Dysfunction or inability to achieve desired erection is a common problem in youngsters. It causes a lot of distress and it hampers marital life. The causes may be a lot- - Most likely cause is Psychological ED, its very common, due to stress, some cognitive distortion individuals fails to achieve desired erection than they used to achieve before. In most of cases all tests come in normal range still they have problem. Depression, anxiety further increases the risk. Work load, stress is also a risk. In most of cases some times the poor erection occur once or twice, but after this individual start thinking again and again about same problem and this increases stress and cause development of performance anxiety and ultimately it again causes erectile dysfunction, and individual enters a vicious cycle of stress-impotence-stress. Best way to deal with it is to talk to your partner regarding your problem, be assured that you are not having any problem, foreplay before intercourse will help. - Second cause is Hormone dysfunction, kindly get your Testosterone levels checked in a number of cases of real erectile dysfunction testosterone levels are in lower range. But as you were having normal erection previously, it is rare to have this cause. - Erectile dysfunction may occur due to chronic illness, prolonged drug therapy etc. So dear friend as your age, height and weight is in perfect range so be assured most likely there is not a big probable try to deal with it smartly. Treatment options includes Management of associated depression and anxiety, newer medicines as Sildenafil, Tadalaphil have promising results (But to be taken only by advise of a doctor). Thanks hope I cleared your doubt.