The thing is, severe pain *causes* nausea for me; it's the nausea that distinguishes "I can take this" pain from "I can't take this" pain.

I've also had more bad experience with nausea -- I had labyrinthinitis issues for a while, and I've passed out from blood pressure drops accompanied by nausea.

In the end, though, I'm not sure pain vs. nausea is the important axis for me -- what's important is acute vs. chronic, psychologically intrusive vs. disassociatable, acclimatable vs. unacclimatable. I've never been able to disassociate nausea (though I've also had chronic undisassociatable pain.)