I think that you are getting some great advice by folks.
I insisted that my wife get a medical check up as her heath was/is important to me. While she fought it, she ultimately went to a doctor and that plus some other things helped rebuild our relationship.
One of the things I heard on a medical call in radio show was a doctor saying that 50% of the men over age 50 have some form of ED problem at one time or another. He was trying to explain the huge numbers of people taking ED medications like viagra etc. and how really huge a business it is.
Your husband at 42 seems a little on the young side, but there are lots of significant medical things that are often associated with ED that are life threatening. Specifically a lot of circulatory/heart disease issues can cause ED as well as things like type 2 diabetes. While you husband may not want to medically address the issue, he needs to as it could be life threatening.
As was also pointed out it can be fueled by the attitudes of a spouse and self image.
Challenging him by asking him if he would mind your having an affair, isn't the approach I would advise. He is obviously hurt on a very deep level. He needs to feel loved and get past his hurt/depression/anger and move on with living life to the fullest. I am sure that you want your partner back so that you can live a full life.
My heart goes out to you. Recognizing a problem is the first step in addressing it and changing your situation. Good luck to you.
>43 years of marriage--My wife and I are now closer than we have been in decades. I believe that my SSM is over.