What Causes Body Aches In Lower Abdomen And Legs?

I have body aches in my lower abdomen and legs. Although I had flue symptoms of headache, lack of appetite, one time 100 degree fever, and general exhaustion for the last 4 days, the skin is sensitive and my muscles are so sore that it takes effort to walk. My wife says this is just flue symptoms affecting a weakened body. Is there any chance the pains in my legs and sensitive to the touch mid-section of my body is more serious, or when should I become really concerned if it is not just a result of the flue?