Sounds like he's suffering with health problems like chronic fatigue and low libido and therefore for him to change he would have to take action and impove his health. If you really love him and want to make it work then you can suggest some ways he can improve his health, CZ is an excellent place for this, but if he is not interested in trying it may be time to find someone else. There really are no tricks in a situation like this, the problem is from him. He is not able to participate in an important part of the relationship and if he wants this to work he needs to take action to fix it. Hope it works out for you.