If you are or are thinking about breaking down in tears, I think that's a signal that you need to take positive action.
Exercise/writing a list of things you enjoy and making sure you do at least one of them every day of the week can be helpful in getting you through. But it may not necessarily solve the problem.
If you go to see your GP it's very possible he'll give you time off, which IME can invaluable in giving you a break, time to think things through and make decisions about your future
You may also want to consider some personal reading – self help stuff or even a counsellor.
I have a thoroughly manipulative boss at work, and nearly lost it last week. A single session with a counsellor and reading a book on dealing with bullies has helped me understand there's actually a huge amount about the situation that's within my control.
Hope this helps