how do I convince my husband to get help for ED?

My husband of 11 years has always had a low sex drive. We have gone for periods of 4 months to a year without sex and he doesn't care. I initiate most of the time as he so rarely desires it. I learned to live with this but now, even when I initiate, he doesn't get hard. Sometimes he gets semi-hard but not for long and not hard enough to penetrate. I have tried everything I can think of to convince him there is a problem but he won't talk about it and won't go to a doctor. I can't live this way anymore. It is affecting our marriage in many ways outside the bedroom too as we no longer have intimacy. HELP!!! (BTW he is 34, takes no medication, and appears to be in good health)