I understand your frustration completely. This is not an uncommon complaint in a relationship & needs to be addressed before the partnership crumbles into non existence. Men are still very career orientated & want to be able to provide for their family down the road which puts a great amount of pressure on them. Is this job something that he really wants or is it a means to an end strictly for financial purposes? If he is just going to work to pay the bills, he will be unhappy until he changes his job. If it is because he is doing some new job within the company that is causing stress due to a higher pressure to preform, it can very easily cause anxiety & unusual fatigue. This often subsides once the initial learning curve is over.
The question to ask him here is; Does he see himself in this job as a long term career? If he answers no, then he needs to get out of it soon for health & relationship reasons. Being tired, having a low sex drive and not having any other interests due to a demanding or unfulfilling career is not good for anyone. (Women are also guilty of doing this.) He could also be blaming this on his job when in fact it is not related to that at all. He may be going through some form of depression that you are not aware of.Find out what the root of the problem is and offer some conversation to help him get on another path. ( He could take a night course or obtain a certificate in another type of business.) Leave sex out of the equation right now and just talk gently to him about his desires. He may be feeling pressure to perform in all aspects of his life right now & it could be a little overwhelming for him.
This doesn’t mean that you have to sit around waiting for him to come back emotionally or physically. Weigh out all your options after a few discussions with him about what he really wants in his future. If he is not willing to open up or understand your feelings of concern, you will then have to decide how long you want to spend waiting for him to be present in your relationship again. You may need to start going out & doing things without him which could wake him up a little. Making him realize you are living your own life regardless of how removed & complacent he has become in the last few months could eventually help him to see what he is missing out on.
Do not give him an ultimatum or try to make him jealous, just go out & do the things you want to do. After all, it is your life too. It may jump start him into seeing that he needs to “step up” if he wants to continue a relationship with you and if not, at the very least you are living your life and not solely basing your happiness on his present existence. Please keep in touch & let me know how things go for you.