The first thing you have to do is to accept that there is a serious problem here, and it's just not going to go away. That being said, I see two possibilities-One, he has erectile dysfunction and is covering it up. Two, he has some psychological issues about sexual activity that he is avoiding dealing with.
If waiting for sex was an issue of his values, he wouldn't be sleeping with you. This issue isn't going to go away until he takes the initiative to solve it. If he has difficulty with an erection, then he needs to see a medical doctor to rule out a medication side effect or underlying medical condition, such as diabetes. If he has emotional issues that are driving this problem, then he will require professional attention for that as well. Since you don't mention other problems, I"m presuming we're not dealing with disabling depression or anxiety. Therefore, I would recommend a therapist specializing in sexual issues.
In my business, I can' t make a lot of guarantees, but I can guarantee that this isn't going to get better unless he is willing to take drastic action. You can counsel and support him, but you can't do it for him. What you can do is refuse to accept responsibility for a situation you did not create.
If he refuses to do anything about the problem, then you are faced with the option of accepting a sexless relationship or moving on. I know that's not what you wanted to hear, but it's real. It's time for you and him to have this conversation.