Hello
Since you are having fever (high grade ) for 4 days and taking
paracetamol . When paracetamol , fever subsides and returns , as soon as effect of medicine is over.
Also having pain in the neck on the right side ,near jaw line, such type of symptoms may be due to these reasons, these include:
1 Mumps , although it is uncommon in 40 years patient , but we can't rule out because pain is on jaw line . Diagnosis can be confirmed by physical examination.
2 The next reason of such fever may be
meningitis , diagnosis can be confirmed by
lumbar puncture ( rare possibility because short duration of fever).
3
Rheumatoid arthritis , because you are feeling pain in the neck , may be a cervical joint pain. Diagnosis can be confirmed by blood for R A factor.
However, there are so many other reasons of such fever like
malaria, flu , so consult a physician and get his opinion because physical examination is important in such cases.