You may want to speak to your therapist about fine tuning those meds. You are on alot of stuff and still hitting the bottom as hard as that, there is something not working correctly. You should not be shooting to high or too low. That is part of the function of the seroquel, to control the mania. The higher you fly the lower you fall. I know all too well and it sucks when you are working and it happens. It doesn't matter what shift you work, I worked morning shift and found myself crying in the bathroom in between clients. How you feel doesn't stop because of what your doing. I would work with the meds and see if you can change something to keep this from happening. As far as your employer, you may or may not get your job back since you walked off without an explanation. They are not legally obligated to give you your job back doctors note or not. I would speak to your boss alone and if you chose to disclose, make sure that the disclosure does not go on any employment records. Tell the person this is just a verbal disclosure that you don't want it on any employment records or indicated in any reference. Good luck and I hope that you can overcome this and stop harming yourself. I am glad you are trying to stay close to your mate which is very difficult when your feeling bad.
Peace