You might be having the problem of erectile dysfunction. Occasional erectile dysfunction may be common sometimes due to stress, or during emotional and relationship difficulties. There are various of factors responsible for it and also may have some underlying disease. So detail workup is necessary to find out the actual cause and treatment accordingly. You may try some pelvic floor strengthening exercise and change your lifestyle, reduce anxiety and stress. If its trublesome again please visit some doctor again and have further evaluation! Thank you!