My condolences to you .
What you're feeling is normal , my Mum died 11 years ago and I remember feeling exactly the same .
In the time before she died ( cancer , so we knew ) you're so tied up in their last days , then theres the stress of the funeral , then it's like you draw a line under the life and feel you need to move on . But it wears you out .
I tried to keep busy , it doesn't work . You need some time for yourself , to regain your strength , and have time to grieve .
I don't mean weeks of rest , but I found even 15 minutes , peace on my own in my bedroom helped . Not every day but just sometimes , I just needed a bit of space and quiet .
It is normal , if you say " Mum died a little while ago , but I'm coping really well " , that would not be normal
Think of yourself sometimes , just have a little sit down ..