My release of ejaculate is delayed causing the penis to go flacid before any orgasm is achieved for both of us - frustrating, and not helped by 'Viagra.'

I have noted in recent time a lack of sensitivity on the head of my penis - I am uncut and have tried a lubricant (Durex 'Tingle') but with minimal increase in sensitivity. Masturbation seems the only way, but my wife finds that practice distasteful. Help!