Jimbo: Alan:
You don't give too much information as to any lifestyle, age, health or other issues/situations that may or may not have an effect on your potency problem.
Rather than ramble about the various causes, it would be very useful if you could answer a few questions:
1. are you totally impotent without viagra or are your erections just less firm than they used to be without it?
2. did you start pumping in an attempt to assist in increasing blood flow to improve erections or did the erectile problem appear once you started pumping? Impotency could be the result of overpumping, since a firm erection depends on the pressure exerted against the tunica surrounding the erectile bodies and if this tunica is overstressed, it can become weakend to the point of not providing this firm sheath needed to maintain the proper tension for a firm erection. The cure is usually to lay off pumping altogether for a few weeks to allow the tunica to "firm up".
3. your age
4. are you a smoker? use any kind of recreational or other drugs that may have impotency side effects?
5. are you going through any kind of undue stress? (job, relationship, etc.). Have you felt seriously depressed about something?
6. was loss of potency gradual or more sudden? Over what period of time???
Lastly, your doctor's point that larger dicks seem to have more problems maintaining erections as we age is not too far from the truth. Over the various incarnations of the LPSG i have communciated with guys that have had problems in that area and for the most part they were owners of LARGE (10" and over) units. As the erectile tissues and mechanism becomes less "elastic" and arterial plaques set in as we age, all else being equal, the body now has more work to fill up the volume required to erect a larger penis. These guys by the way notice declines in erectile strength in their late 20's and 30's. Although your length in NOT in that category, your girth may make up for the length as far as the overall VOLUME of your penis is concerned. (by the way, what is your UNPUMPED girth? and what size tube do you use in your pumping?)
Jimbo