I am sure you are worried sick about this but hope you have visited an Infectious Disease or GUM specialist to get the whole range of STDs checked out.
Of course, the HIV 1 and 2 ab test is the right test given the time frame (when antibodies
to the virus would have formed IF you have the reaction, but clearly not so) but the most sensitive test remains HIV PCR or Viral load
if you had more encounters since.
The feeling that you describe can be scabies
but would be evident on clinical examination, although a rash would mean this is urticaria
. House dust mite and sea food allergy
occasionally come up positive on blood tests, so if you really have reactions (allergic) when you have sea food the result is correct.
You need a throat swab, HIV PCR/VL and get seen by a specialist to lower the apprehension and hope things turn out well.
As per the urticaria, long acting non sedating antihistamines for 3 months is the treatment.