What Could Fever With Chills Ring Menstrual Flow Suggest?

I had a fever come up out of the blue, with chills and no sinus problems etc...an hour or two later I started my period. I had an on and off feverish feel for 2 days, and then it went away. I have no cough, or any other cold symptoms. I did have body ache all over, and my stomach hurt a bit. That was about it. What is that?