A woman can make 4 babies with 4 different fathers in 9 months, right?

Someone decided we need a "rubber band programmer" who bounces around from project to project as needed, and that gets to be me.

So I work on 4 projects, with 3 programming languages, 4 frameworks, and with users in 4 complicated industries, none of which I have experience with.

And my boss wonders why I'm not as productive as everyone who has worked on 1 project for 5 years.