Firstly, be kind to yourself – it's utterly and absolutely normal that your head is still spinning, and it all seems too much.
I have not had the horrifying shock that you have, but I have had the whole load land on me when my husband's mental health fell apart. For the day to day, stick to a routine as much as you can, and simplify where you can. Right now, good enough is good enough.
For the big picture, I found it helped to try to take one or two steps forward each week. Some weeks, I managed more; some weeks, one small thing was a hard-won achievement on top of the day to day. Reflecting on what I had accomplished each week really helped my mental health. The situation was still very hard and overwhelming at times, but I was taking steps forward.
Seek support from friends and family if you can – emotional and practical. Judge who you share such painful news with, yes, but if the answer is 'no one', that's probably not sustainable. Are there any professionals involved, or have you got a good health visitor? It's worth asking if there are any charities that help support people in your situation. I got some support from one, a weekly coffee and chat, and it was really nice to have that space. I'd also ask your GP for a referral for counselling, or again look at one of the charities. Given what you're going through, a place to work through it all sounds like a very good idea.
And again, be kind to yourself when you can't do these things. If you got yourself and your toddler through the day, sometimes that has to be enough.