I have a problem that I don't understand and is very frustrating. I am 41 years old and I get great erections if I masturbate, and I typically orgasm quickly. When I am with my girlfriend or other women, I don't get a great erection and if I do, I will often soften during intercourse. I have tried Viagra and I get great erections then most of the time, not always, but most of the time. And when I do use Viagra, I often won't orgasm, or only seem to orgasm after a couple of hours and tons of effort. It's very frustrating and at times makes me avoid sex and just look forward to masturbating. Masturbating is easier, but I truly had much rather be having intercourse with a woman. I don't understand why I get such great erections alone, but feel like I need Viagra to achieve an erection with my partner. HELP!!