Depression.
Sometimes, I sit for hours at my laptop in my room in complete silence. It's not that I don't have music playing; it's that there's musical rambling going on inside my head. I have spontaneous music in my "mind's ear" near-constantly, and this has been the case as far back as I can remember.
I never stopped making music. I just stopped being able to share it with others like I once could. Each change of treatment is a fresh attempt to reclaim that ability.
Maybe this one?