Marnes, have you guys told your 11yo?
Here's how I told my 19yo: he helped me plant an arbor vita one day in the fall and he helped me a lot -- e.g. lifting me up by my underarms when I was too tired and weak. Digging, adding soil amendments, etc., etc. We went inside to take a water break, and then we were going to put in the other thing I had bought -- a red climbing rose. I said, "I guess you've noticed that something is kind of weird with me (speech slurring, weakness). I don't have an official dx yet, but I personally am pretty sure. It's probably a neurological condition. Some people progress quickly and some people slowly. I don't know how quickly I would progress. There's no cure." Tears started rolling down his cheeks and I stood on the bottom step of the stairs to make a hug more comfortable -- he's 6'3" now!
You might not be ready to share the news with her yet. For now you might be more comfortable telling her something briefer -- e.g. "I'm very sad about something personal. I don't want you to feel that there's something wrong between us. I need to cry a lot and be sad, for now. I don't want my sadness to be contagious for you -- so I thought it might help to tell you what's going on with me." Or something like that. You could write it down if you can't spit it out, or you could ask your partner or someone else to help you.
Children are often amazingly perceptive.
Okay, enough about your daughter. Now I'd like to focus on you. Have you and your therapist identified any settings or activities that help you feel better, even if it's fleeting? For me, it's puttering around in my garden. In winter I like to look at the structure of trees without the leaves. I like to look at them in different sky and light conditions, but my favorite is twilight.
I do understand how you feel -- it is definitely devastating news -- but I'm concerned about the overwhelming, relentless sadness you're describing. Would you mind doing me a favor? Go to a walk-in or ER, or book a sick appt with your primary, and show the provider some printouts of some of your posts here? I'm concerned about the depression you may be in. Remember, a problem share is a ... I can't remember how it goes after that.
I hope you can find some relief and eventually some joy in life again.
Regards.