Jamie,
It is my worst nightmare. In 2000 I survived an accident and was told I would never walk again. My reaction was to tell me partner that I never in a million years wanted to put him through this, and told him he was free to leave. That was really stupid of me, but I saw no future.
You see a future, and for him that is vital. My advice be there for him and do what you can do together. He will undoubtedly need to experience your partnered love making, but perhaps in a diminished capacity.
Temptation is to deny your grief. I hope as you become more experienced and practiced you can do just that, but for now, of course you will cry and perhaps you will have more crying jags. Do not hide that precious gift of obvious love from one another.
There is seldom anything that can be said, for one's words contain no magic, so practice touch. Treat him as much as you always have so that he does not sense you are afraid that you will hurt him, for what more hurt can he really experience.
Practice with each other holy presence, and do spend some time recallomg favorite old memories and times, for when he is gone, you will not have anyone left to share them with who can truly share them as you do together.
Be sure when you are able to understand clearly what each one needs from the other as far as ceremonies when one dies, and it will be as much funeral for you as it is for him, for what happens to our partners in a way always happens to us. Also with gay justice in the sorry state it is, do make certain of your inheritance and whatever else is important and necessary.
Please know that our hearts reach out to you, and I am fighting back tears even now, for this is truly a difficult time, but you will be able to live it, one day at a time. Thanks for sharing this important information. You are a wonderful person, and I wish you the best, and you may PM me anytime you feel you need to. God bless.
Shep+ 
