I am new to this forum and so far I have read about 20 topics and they all lead to the same problem --- your diet, which can be corrected quite easily with the proper program and your dedication. For example, if you always eat fast food and junk food, your penis will become useless (as you've seen in "Super Size Me"). Chemical imbalance in our brains leads to impotence. Poor blood circulation leads to penile dysfunction (due to lack of blood flow to your penis). Most of these "problems" are often diet-related. I see most of you want to solve the current problem, yet you have forgotten it took you many years to become the you are now.
One thing I would suggest is see a nutritional consultant and get your eating habits fixed. Doctors diagnose and treats your current problem, however, they lack the proper knowledge to keep you healthy. To those who are still reading this, I am here willing to help those who needs my suggestion. So don't hesitate to e-mail me or PM me. I can HELP.