Just got over a similar situation where I broke up and was still living with my ex; this would be bad enough, but she also began spending all her time with another roommate, perhaps romantically perhaps not, while excluding me from all communication. She could not afford to move out, and I could not afford to help her move out; somehow I held on to empathy to allow her to stay.
I worked from home about 50-50 before this. As you may imagine, concentration and focus became impossible at my house, difficult everywhere else.
My advice is not meant to be callous, but: grin and bear it. Struggle through, and find the focus within yourself. You'll make it through this, regardless of what happens. How do you want remember making it through?
Some tricks I found that helped me work:
classical music on headphones,
small manageable tasks (decide tasks to be done, choose tasks you're doing, stay on target),
mental mantra's ("be vigilant, stay on target", "my time is valuable and irreplaceable" both did me well),
meditation (seriously; 20 min at morning and night thinking about nothing but your breathing does wonders to let you focus).
Spend free-time with empathetic and sincere friends (not coddling; the goal is not comfort but mental digestion and moving on emotionally; if necessary, seek professional counselling),
exercising,
and lots of outdoors (helped me put things in perspective).
I also found the poem 'Desiderata' by Max Ehrmann to be a big help (to each their own.) I've put the lines that helped me the most below:
"Many fears are born of fatigue and loneliness. Beyond a wholesome discipline, be gentle with yourself.
You are a child of the universe, no less than the trees and the stars;
you have a right to be here.
And whether or not it is clear to you, no doubt the universe is unfolding as it should."
Above all, forgive yourself for feeling like hell. It's expected, and acceptable. Best of luck.
EDIT: Formatting