I was just running and flying like a bird, so much energy that I could…

I was just running and flying like a bird, so much energy that I couldn't stop. Now I have sudden extreme tiredness. I don't want to do anything, only sleep and lie down. I barely get out of bed for even scheduled appointments. Since New Year's Day, I've been outside only four times, and already on January 12th ? and even then, most outings weren't longer than an hour. Does anyone else experience this? I fall asleep while walking.