Hello, I had unprotected sex-am a male-with a woman 6 days ago. This was my first partner in 7 years and previously only had one partner. About 4 1/2 days later I noticed a red rash (slightly raised) near the base of my penile shaft. It still remain

Probably not an STD. No STD causes this sort of rash or in this location. If primarily blisters that become pimples then open sores or scab-covered, herpes would be a concern. But this sounds more like physical irritation, allergy (e.g. vaginal hygiene product), or a superficial non-STD skin infection, e.g. fungal. It doesn't sound worrisome, but if it continues or you remain concerned, see a doctor. Good luck!