Thank you for contacting healthcaremagic. I have gone through your question and understand your concerns. Let me know if you can achieve and maintain a good quality of erection in sleep, in the early morning, during masturbation but not at the time of coitus? If you are able to achieve and maintain erection in any one of the above mentioned situations than your problem is more likely psychological rather than physical. Sex is largely what happens between two ears and not that happens between two legs. An occasional episode of erectile failure due to functional or situational reasons like fatigue, tension or own pressure to perform rather to enjoy is very common. This is the most common cause of inability to achieve or loosing established erection during sexual intercourse with partner. This failure of erection makes one feel I should perform best and he tries to erect’. This in turn further leads to lack of erection as mind gets anxiously diverted towards own performance rather than enjoying kindling. Some common causes of erectile dysfunction are:- 1. Diabetes 2. Some medicines like anti depressants and anti psychotics 3. Hypertension 3. Performance anxiety (the most common reason as I described earlier) 4. Alcohol use 5. Smoking When similar patients come to my clinic I prescribe them Sildenafil 50 to 100 mg to be taken 1 hour before anticipated sexual activity. But it should be taken only under medical supervision as it can be harmful if taken in extra dose than needed. I also suggest them sensate focus exercise. You may read on internet. For helping you in the best way, I recommend you to consult a psychiatrist well versed with psycho sexual therapies. He will definitely assist you to find out cause of erectile dysfunction in your case. Wish you good health.