One of the truly pro musicians I know once told me that he had 62 W2's from the prior year - 62 different clubs, churches, bands, etc. had paid him to perform, arrange, or whatever he did musically for them in one year. Although I often think simplification is helpful, in the music business, diversification is more where it's at.
I'm a volunteer, and in a typical year, I play at 6-8 churches - I'm pretty small potatoes at diversification, but there are times I do understand your dilemna - too many directions calling me for the same date. Still, if I want to play at places, I have to do my best to say yes to as many situations as I can - your gig calendar (which you need more than I do, if you're going to make a living at it) needs to be pretty full, and that's unlikely to happen with one or two bands.
The thing you have going for you is that you're a bassist. We're few, far between (at least the good ones) , and typically more employed than most musicians. Work with that.