Respectfully, the only person who knows what is up with him is him!
I suggest next time you speak to you him you ask him if there is anything you can do to help him with all the things that are going on and arrange your next visit to him or his next visit to you. If he is reluctant to do that then I would advise you simply agree that perhaps now is too stressful a time to organise it and when he's not so busy if he gives you a call you can chat again. Remember to put the ball in his court every time. It lets him deal with the stress of house buying without having any added stress from you. If you don't hear from him, don't worry about it. Give him time and space to deal with what is happening.
Once the house buying process is over then you can reassess what his feelings are because then he should be able to find time to call you and see you and not give further excuses. If he then makes further excuses, you may need to ask him if there is a problem, if there is something he is afraid of or something he needs, that he has not communicated with you. Try to let him speak without interruption and listen to what he says. This way you will hear the truth and not just transfer of stress from the house buying process.
Working so many hours and dealing with house buying, may make him very tired and very stressed. Mostly at this time, my view is that you need to be patient. Time will make apparent what is going on. Take some deep breaths and just get on with your own things, even mundane things like tidying, cleaning, washing, or going out with friends, going to sporting events, or reading a book. Focus on yourself and remember that whatever happens, you will be able to deal with it.
All the best,