It is my privilege to be able to help you,
I have gone through history as you had night sweating which if followed by severe muscle ache and swollen lymph nodes
in the neck.
I suspect that you are having a viral infection and the symptoms are in favor of viral infection.
As your treating doctor has advised some medicine to control infection in the body, you may require some medicine to reduce the pain and stiffness
Consult your Physician for the stiff neck
and he will prescribe some medicine to reduce the pain.