What Is Causing The Flu Like Symptoms I Am Experiencing ?

Felt fine in AM, went to senior exercise class at 8:45am , and planned for activities at 1pm and dinner with AARP at 4pm. Lo and behold about 10:30-11:am, I was hit with extreme tiredness/muscle weakness, chills, and a bad headache. It s 7pm now, and I ve taken 3 buffered aspirin , which helped the headache (but it s still there), but still feel somewhat weak when I usually have plenty of energy. I have no upper repiratory symptom, other than excessive eye watering when the attack was at its peak, and occassional sneezing that feels cold like. I m a female, aged 70 next month, and I ve had a flu shot, which I think also included H1N1 vaccine (don t recall exact date). I am in generally fair health and visit my physicians [number of chronic conditions such as hypothroidism, high blood pressure, gastrointestinal/ GERD , prior B-12 deficiency, which are well controlled by Synthroid , Cytomel, Diovan, Pantoprazole, Follbee, & ( Premarin , because it improves my memory and mood)]. Had Lyme s disease in 2007, and live in area where deer still abound.