Anonymous“ a. I'm
so much behind with my work.
b. I'm so behind with my work. ”
Hi,
b. is better, but probably not for the reason you'd expect.
In this expression, "behind" works like a place rather than a quantity. We'd say,
"I'm so far behind in my work!"
I use the exclamation point because "so" will not make this a declarative sentence. But you may say,
"I'm very far behind in my work." (That's a legal declarative sentence.)
"I'm so behind with my work!" is okay, but "in" is more common.
"So" in a declarative sentence would be,
"I'm so behind in my work that I'm sure they're going to fire me."