Carol, if you can feel where the next note should be, does it mean you learn more by touch than sight or hearing? It's hard for me to imagine not being able to "hear" things in my head. It's more like imagining a tune, though. Of course, I hum or whistle all the time. The imagining is almost like humming without actually making a sound.

Can you close your eyes and imagine playing? Imagine when and where your fingers go? I'd think you could use touch the same way folk use sight and hearing. The easy way to improvise is to know where the notes to a chord are, and try different notes in that chord instead of the melody note you usually play.