Hello
As you mentioned that you are having recurrent mouth ulcers and
sore throat . No doubt these two symptoms are among few symptoms of acute syndrome of HIV infection . Others are fever, pharyngitis ( as sore throat , in your case)
lymphadenopathy, headache. retro-orbital pain ( behind eyes) , arthralgias/myalgias , lethragy/malaise, anorexia /
weight loss, nausea/vomiting/ diarrhea.
Erythematous maculopapular rashes, mucocutaneous ulceration ( as in your case ).
Antibodies to HIV begin to appear within 2 weeks of infection ( as you got a test after 20 days , so this must be specific).
Western blot P 24 rapid nucleic acid amplification ( pcr , rna ) is most specific and sensitive test , accuracy is 99.5%.
Now question about sore throat and ulceration , this may be due to
acute pharyngitis .
So in my opinion don't be desperate and get in retest .
Hope this will help you.