Fatigue, Pain In Right Forearm, Wrist, Knees, Shoulders, Headache, Feeling Ill. Healthy Lifestyle. Tested Negative For RA. Reasons For Symptoms?

Hi, I am being referred to a rheumatologist for symptoms that include fatigue, constant pains in my right forearm and left wrist (difficulty carrying groceries, etc.- no injury-) pains in knees and shoulders at times, headache most all the time and general ill feeling. I am 42 years old and have always been very healthy until about a month ago. I've always gone to exercise regularly at the YMCA, taking classes such as zumba and light weights. I have always been energetic and healthy. Now I don't feel good or like doing much of anything. I began to notice a weakening of my muscles around Dec. but didn't feel tired or have the pain in my forearm and wrist. All my blood work has been normal in the normal range. Tested negative for RA. Why am I experiencing these symptoms? Am I missing something that could be causing these symptoms? Thank you!