OK, so I got to be the patient this weekend instead of the doctor. I've had muscle aches all over my body, like restless legs gone crazy. I've also been very nauseated and had fevers off and on. My family will tell you I've been grumpy, too, because it hurts to move and it hurts not to move, all at the same time.
So, if your little one is extremely grumpy, give him or her a break. Maybe they need a nice, warm bath, or just a hug and a story. I know I do!