What Causes Fever With Chills And Sore Throat?

Hello there. I have a really bad headache and aching muscles. It is difficault to turn my neck because of the muscle pain. I have also had the chills a lot and a temperature of 39.6 C. I have a very sore throat which is very red and swollen. I had really bad abdominal pains and went to A&E on sunday. My temperature was only 38.4 C then and I was not feeling as bad as I do now. The doctor there told me to take Gaviscon but I have deteriorated since then. Do you have any suggestions as to what it could be?