So sorry for your loss OP
grief can cause very physical symptoms, feeling emotional is very tiring, as well as not being able to sleep, the grief is on your mind the whole time.
When we lost MIL, we all grieved in our own way, it was a horrible time, my eldest DS, back suddenly went he couldn’t move without pain, when I spoke to the pharmacist, about buying some more effect pain relief, she was really concerned said he should see the GP, as such a sudden onset. She asked if he had done anything different that could have caused the back pain, I told her his beloved GM had passed away a few days ago, she said that is probably his bodies reaction to it. I fully believe that to be true, he never had back pain before or since.
DS1 is the more sensitive and quiet one of my two sons, he said the the ball in the jar, exactly described how he was feeling, just overwhelmed by his feelings, the grief was all consuming.
You won’t feel like this forever OP, as time passes by, you will still feel sadness at the special anniversaries, but you learn to live along side the grief. That takes time, my advice would be not to rush, cry when you need to, don’t compare your grief with others in the family, that may look ok on the surface, as they probably don’t feel ok. The trap we got into, was trying to hold it in, as not to upset others. It’s a really tough time, accepting that life will never be the same again. But you will get through it, once again so sorry for your loss.