My experience with Viagra pre-op, is it gave me headaches and indigestion, so I stopped using it. But, everyone is different, so try it?
Prior Doc gave me a sample of Staxyn with instructions to take it on empty stomach and an hour before sex. I tolerated that very well and was pleased with the results.
It does sound like you're doing great! Do seek advice from your urologist. If he/she doesn't have any good suggestions, don't be afraid to seek a second opinion.