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remains negative after 3 months and even after 6 months gauranteed that you are not having HIV.The results are more conclusive after 3 months itself. If it came negative for two times after 3 months then there is no further test is necessary. Just forget about HIV due to your past activities. All your symptoms are not specific to HIV and may be due to some other cause.
Consult a Dermatologist
, he/she will be able to guide to get treatment for your rash
on your back.