I would suggest that you are both have to think about how things can change. The thought that he will be retiring at some point in the future, may be something that is now becoming a thing that may not have been thought about a great deal by either of you. Also it does sound that you are quite depressed in general. So I think you could first of all try and see what you can do to change your own life. Look back and see if there was something you enjoyed doing in the past , but that you no longer do for what ever reason. I agree that swimming would be very good to consider. It is something that helps me physically, but also mentally, as I nearly always feel better for having gone , and also if you make that a regular thing, then you dont have to decide - shall I go swimming? because it becomes something that happens on tuesdays or whatever. You then meet other new people swimming and sometimes this can lead on to other things or having coffee together. If you can do something like that or gardening or whatever appeals then you begin to get your own interests and so will not notice or rather will not resent what your husband does with his time. If you can sort some things for yourself first, then you can find a time when you can talk with your husband about what might change when he retires, but not in a negative way. More looking at what you may now be able to do, such as travelling for a longer period of time and not having to cram things into a 2 or 3 week patch. So you might write down a list of anything as it comes to your mind, of possible things you might enjoy together. You could perhaps suggest that you have a couple of long weekends doing something together, whether it is a small course that you might take together or visiting somewhere that you have always said you wanted to go to but not yet visited.
I do think that finding out what you like doing and looking up any courses that are all starting at this time of year, so you might go away for a weeks course in whatever you fancy. You will learn something, meet new people, and come home with something interesting to talk about . You can take some time trying out things before you really get into talking about how you both see the future happening. You may still be able to be happy with each other doing your own thing, but sharing time together too.
If very sadly you actually find you either have nothing to share and enjoy any longer, and you literally have no life to share at all then it may be that you decide that it would be better to split up and live your own lives but you could then part in an amicable way and still keep in touch. To me that would not be what I would want, but far far better than having a totally miserable life, where every day is lonely and no one is able to enjoy anything. But this is something that only you can decide. At the moment, starting to enjoy your own life more , meeting friends, go and see an art gallery, go off to the cinema or whatever. Sort of think that you are giving yourself a little holiday for a fortnight and dont feel guilty about doing the things you want to, go for a walk, wear the clothes that you keep for best , stick a pin in a map and drive to a new place you have never visited. Even if you come back from something thinking never again , you have still made an effort and often you will then think I would rather have done X , so that will show you where you might go next. I wish you the best of luck and hope that you find a better way of life.