Bereavement

your loss. Hospice normally has a service that you can call and ask to speak with someone or a group you can join. I know that may not sound appealing, but consider it.
As far as your Mother getting a clean bill of health. It might be your Mom said nothing to her doctor about problems she was having. You would be surprised how many people ignore symptoms or say nothing to their doctor because they are afraid.

I lost my Dad in August, but he was in his nineties and yes it’s sad, but he lived a good long life.
Holidays seem to make things even worse for those missing their loved ones. Please consider getting help. I don’t know if this helps, but just think about it.