Thanks everyone. I ended up trying the Ambien with extremely bad results (never actually fell into a deep sleep, just hallucinated all night and woke up every few minutes). I think my body eventually gave out as I managed to fall asleep without medication last night besides the OTC melatonin I've been taking. I slept fitfully and woke up every hour or so, but got in about 7-8 hours for the first time in a week.

The mindfulness and breathing exercises are normally very helpful. Unfortunately I felt so exhausted, sleep-deprived and depressed towards the end of the week that I was totally unable to concentrate long enough to perform them. I did some this morning and found them helpful.