Hi Sandy,
As a sufferer of PCa you are entitled to Viagra and/or Cialis etc, but often GP's need prodding before they will issue a prescription, so if I was you I would get off to your GP and get some soon.
Personally I found them a great help in the first few months on HT, although it has to be said that eventually HT tends to kill off your desire.
However it isn't permanent, I do not know how long your Consultant intends giving you HT, in my case it was 3 years in total, and I think the consensus is that you should stay on HT for at least one year after last session of RT?
If you want to understand the science behind it look up 'adjuvant hormone therapy'.
After I had finished 3 years of HT it took a good 12 months before I regained anything like full sexual vigour, and even then I could never guarantee a quality performance, but hey ho, anything is better than nothing.
I think the problem is we tend to look back on our youth, compare our current performance and blame PCa for the difference, if I am honest my powers had been gradually declining long before I was diagnosed.
Best of luck.
:)
Dave