Prayers up.
You have to unwind as well. You stressing out isnt good for him either. Put the energy into making plans for various outcomes. Make plans for what you want to do with him while he’s here. Turn it proactive and productive. It will move you from helpless to in control of what you can control.
And you could die tomorrow any number of ways. Its not a given you outlive him. So calm down. Breathe. They have decaf now. Realize what you are doing is unhealthy for you and him and quit doing it. Make plans for good things you can do and want to do with him, now. Otherwise it will paralyze you and you will waste all the time you still have, and you will then hate yourself for doing that.
You owe him not to stress out and to plan and make the most of the time you twp have.