I remember that exact feeling of, "I don't know how long it will last." In my 30 some year relationship w SO, we have said that "we don't know when the rain will come."
In this situation, I would clean, make soup, do mega laundry, go out to live music and come home and make love.

You need to use some energy for that!
It does sound MS-y to me but I only just read Sparky's link- that does sound similar.
Best to you,
ANN