Try and break things down into smaller chunks to deal with, then things that can wait can be noted down and you can tackle them when you feel able. Maybe get a book to note it all in, by recording it for you to come back to might help ease your thoughts a little bit. Any really urgent items perhaps a family member or trusted friend could help you? Its hard to think straight in the early months of grief and when we are emotional everything is so much harder
I remember the early days, the pain that feels physical, deep inside your core. It doesn't feel like it, and we wish to get rid of such intense pain, but be gentle, it will take time but slowly it will ease. We are always here to listen, whatever you need to talk about.
You can try some breathing techniques for anxiety and panic attacks, by practising them when you are feeling ok can make it easier to engage those techniques during a panic. One technique is called 7:11 breathing. You breathe in to count of 7, then out for count of 11. The idea is to lengthen the outbreath which helps to calm. Can do whatever proportion works for you and feels comfortable, like 3 in and 5 out.
Try and ensure you are drinking fluids regularly (even if you have to set a reminder/alarm to remember to) and try to keep alcohol to a minimum (I found that made me alot worse), and eat whatever you can to keep your strength up, regular small amounts would work well. All the emotions will be wearing you out
Sending a big hug xx