My boyfriend is always tired

My boyfriend of 4 years is always tired and it is really causing issues in our relationship. He never wants to do anything anymore all he does is sit on the couch. He does work out and go to his job where he sits all day but that is about the only thing he ever has energy to do. We maybe have sex once a week at this point. I told him that it is a problem for me that we never go out and do anything id even settle for a date once a week to just dinner or a movie. We have also never been on vacation together. When I ask him he says he would like to but doesn't know if it will ever happen because he is tired all the time. I told him he is too young to be this tired and he won't go to a doctor. I just turned 25 this month and he is 27. I have been with him for so long and I want to get married before I am 30 so it seems scary to break up but I don't know what to do anymore. I feel upset and like I don't do what I want anymore. What should I do?
My boyfriend is always tired
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