Big hugs to you, Winnie.
When my exhusband packed a truck in the middle of the night one day, I thought my world was ending. It was like being hit by truck- no warning at all. I, too, lost all appetite and lost tons of weight (was healthy weight to begin with, and lost until many people started voicing concerns for my health).
As i moved my life forward, my appetite returned and i gained back the weight.
Make sure to look after yourself! The last thing you need is to look like you aren't happy without him in your life, when you have to see him for mediation/divorce proceedings- no matter how you feel inside. At least I felt that way.....
I hated cooking just for me, but found things like making an omelet or grabbing those prepared (just heat and eat) chicken sausages were healthy and on plan.

Stay on plan, it will make you feel more in control and then you won't add "feeling like diet failure" to your mountain of pain right now.
And i would keep a food journal, including your emotional state.....you don't want to eat of boredom/ loneliness/ feeling sad or angry.....

Since you have bipolar, i am assuming you see someone? I think therapy is so valuable for anyone coping with divorce, so I am glad you have someone to trust.

So very sorry to hear this, but I have to say looking back- it was one of the best blessings in disguise i have ever had. I am now married to my real life Prince Charming, who finds ways to show me he loves and appreciates me EVERY single day.
In the meantime, maybe you can make some new friends (meetup .com is a free website to bring together people with shared interest. it is NOT a dating site. I joined a ski club and a hiking club and met many new friends. it was a great way to start to feel better).