There's some wonderful advice here - some of which I've used in the past to get out of a 'bass' rut, or as one of the contributors more incisively says 'music' rut. And it never hurts to put the bass down for a week or so, and play 'bass' without it. Can you play whatever you whistle, hum, sing, yodel, clap? Go for a walk in the woods, and listen to what tunes you have slushing around in your head. What's your natural key? If you'd been born before bass guitars had been invented, what sort of music would you make? Just some ideas to help lift you out of 'stuck'. Good luck