Cause of Night sweats for 5 months, off work - any ideas?

I was innocent party in serious car crash in Feb 07 and suffered multiple fractures in legs. I did over 600 hours of physio to walk again and went back to my great office job few months later. I could just about cope with it. But suddenly I woke in March 08 soaked in sweat. I've sweated really bad EVERY night since and also if I sleep in day - but not if awake. I've no energy in day so unfortunately had to give up work! Baffled Doctors as had blood tests, CT scan, checked medications and combinations all OK. Docs thought initially was stress induced dreams (PTSD) but after this long they are testing for physical reasons but nothing found yet. It's not menopause - I'm 50 but male! Its stopped my life just when I'd got it back on track. Since this outbreak of sweats I have to take anti-depressants. Any ideas please?