I'm pretty sure you "bleed", not sweat, like a stuck pig (stuck with a knife or some other sharp object). That's a whole lotta bleeding. I think you just sweat like a pig, stuck or not. Although the pig was probably sweating a lot before he was stuck, I know if someone was coming at me with a big knife, I'd be sweating, too...
I feel like an ass. Not because she's right and I wrote a whole entry based on a euphemism that never existed, but because...well, okay, that is the reason.
But at least I wasn't bleeding.
Let's say I was sweating like Sylvester Stallone in Over The Top. That conjures up a nice mental image. Now let's put that Over The Top Stallone character in a prison laundry room getting gang-raped by Mexicans.
THAT'S how sweaty I was.
ADDENDUM:
Actually, the phrase is "squeal like a stuck pig." - Maggie