What Is The Cause Of Someone Taking An Afternoon Nap

What is the cause of someone taking an afternoon nap waking up thinking it is the next day? Was in state of confusion because I thought I had slept in my clothes. Got up and took my morning meds and made coffee. My husband died two months ago and I know I have been going through a difficult time. Could losing him cause me to do this? I feel like I'm going crazy. Thanks,