Venous leaks & being able to convince your girlfriend to stay

Hi, I was diagnosed with venous leaks a few months ago. Does anyone know if these can be cured by lifestyle changes e.g. a lot of physical exercise & healthy diet or do they really require surgery? I have been taking cialis daily but the past few months but have failed to have sex with my girlfriend since last May. Although I can get my penis to be erect for up to a few minutes as soon as I put on the condom I lose the erection. However when I masturbate I can usually get longer erections. I’m really in a catch-22 situation as I need to practise with my girlfriend more often but each time it fails she gets more & more upset & I’m REALLY REALLY WORRIED that she’ll leave me soon! Would be very grateful on any advice on how I could convince her that there is still hope that we’ll still be able to have successful sex soon. Many thanks!