2 thoughts:
1. Go talk to your supervisor NOW (if he/she is someone you can trust). Explain in brief what's happening. Go home get whatever you can quickly and get out.
2. Make it through the day (I know far too well how hard that is) but call the police NOW and arrange for a police escort to get your things. They will go with you so you can get your things and if your BF/H (sorry that I can't remember which it is) acts up, they'll be there so you'll be safe.
Can you do one of those things? I think a side effect/benefit of the police escort is that there will be a documented record that he was in rehab, checked himself out and is NOT safe for you to be around.