Rashes alone do not reflect ARS. You had unprotected sex with someone of unknown health status, over three months ago, that certainly put you at a risk of HIV transmission. However quantum of risk is not very high from a single isolated act.
Do not focus at your symptoms, they are confusing and misleading most of the times. There is no accurate technique available on the planet, determining the infections from the symptoms. The only way to check our status conclusively is the HIV test.
You may go for an HIV test anytime now, collect your conclusive report and move on with your life. This is the only way to rule out the infection
4th generation is conclusive at any time after 28 days and any antibody test at any time between and after 6 -8 weeks .