Thank you for your query at DoctorSpring.com
The thing about HIV is in 90 % of the cases, it does not show any symptoms or any reduction in blood cells till 1/2 years after exposure. So you can be rest assured that the sore throat you're having is not related to HIV in any way. Moreover HIV at times presents with vague symptoms such as low grade fever and lymphandeopathy ( which is characteristic around the neck ).
Also rapid tests checks for both antigen and antibody. Since it is negative at 54 days, you're fine.
I will ask you to repeat the test once at the end of 90 days from exposure. Once that is negative, you do not need to repeat any more testing. Yes, since your partner had sex with someone who was HIV positive, that puts you at some risk, but let's just say you evaded that. Negative at the end of 54 days, 99 % rules out HIV. Some doctors prefer to see readings after 3 months, hence I asked you to repeat after 3 months.
Muscle aches could be due to the infection. Nowadays most infections are resistant to contemporary antibiotics and hence takes longer time to recover. You can proceed with second course of antibiotics.