Since you said that you have rash ( I’m sure that you misdiagnosed the rash , because I don’t think that’s rash) and the most important fact is that the ARS never show up 5 month post exposure , they occurs in 2-4 post exposure and the symptoms never show up isolated. I’m not saying you don’t have hiv , you must get tested and stop diagnosing symptoms , any HIV test now will be conclusive .
A one time unprotected sex exposure has about a 1% chance of transmitting hiv. It's very very low. And I would not suspect pimples on your chest to be HIV. You most likely do not have HIV from that one episode. Biotin has to be taken in huge quantities to in very large quantities well above the normal dose which I'm sure you don't take. Symptoms are never used to diagnose HIV. Only a test and at 5 months, you can do that and rule out HIV once and for all. So, test to do that but expect a negative.