A Long, Slow Decline - Anyone Can Advise Please?

I'm 66 years old with chronic ED.  It began to arise many years ago and I consulted a Urologist who prescribed 'Caverject' prostaglandin injections which worked but were grossly inconvenient as I was travelling internationally a lot.   Then he prescribed 'Viagra' which worked well with the maximum dose (100mg) for some time.  However, that also lost its efficacy about 5 years ago and as of now, I'm completely unable to achieve an erection.  I've tried 'Levitra' (maximum recommended dose) and 'Viagra (100mg) but without success.  It's also becoming increasingly difficult to achieve erection by masturbation.  I've tried a vacuum pump but that doesn't work either.  When I masturbate - maybe once a week, I can achieve sexual climax and ejaculation but with a very weak 'erection' totally unsuited for sexual intercourse.  The appearance, quantity and consistency of my ejaculate all seem to be the same as they always have been.  I have no pain or irritation during or after ejaculation 

When sexually involved with my lady friend, I get the sensation of being erect but that's all and never any erection to go with it.   I have no adverse symptoms of anything else.  No pains or any particular difficulty urinating - though not as strongly as I once could.  I'm not incontinent at all.  I'm somewhat overweight and I've had high blood pressure diagnosed over a year ago but now under control.  I don't smoke or drink alcohol, nor do I use any form of drugs.  I have Fatty Liver Disease and an enlarged aorta.  I've never had any serious illness.   So far as I know I do not have any emotional cause for this and the fact that I've gone so gradually from being sexually active around 16 years ago, to being totally incapable today - suggests that the cause is a long term physical deterioration of something somewhere.

Does anyone have any sensible if not qualified advice to give me, please?  I might also add that I live in China where I have a major language problem and where English-speaking urologists are thin on the ground.  I've tried various over-the-counter Chinese preparations but they don't work either

Dave