Well, I think I did something to my lower back.
Last week at a party at my SO's house, I stayed over without my ambien(bad idea 1), then went to sleep on a very, very bad bed(it has a metal rod right about where one's back would be) and then went to the gym and worked my legs the next day.
Monday morning hurt a whole lot.
Now it's Saturday and it feels a lot better.
I'll say one thing for sure, I'm bringing my ambien to parties and taking the couch from now on.