Welcome to the forum. Thanks for your question.
The bottom line is that it is statistically unlikely you caught HIV or that you have ARS. Statistically, it is unlikely your partner had HIV; and even if she did, vaginal sex is pretty inefficient for HIV transmission (average 1 in 2,000). And your symptoms aren't typical. About 70% of persons with ARS have sore throat, fever (over 101), and skin rash (all three), and probably around 90% have at least one of these. Diarrhea and other gastrointestinal symptoms can occur, but rarely as the most prominent symptoms. Seven days is early for ARS onset -- maybe possible, but generally it's 10-14 days. Finally, ARS typically lasts 1-2 weeks; 48 hr is definitely too short. On the other hand, a 48 hr illness is exactly typical for the most common causes of viral gastroeteritis -- which probably is what you had. Most likely it had nothing to do with your sexual encounter 7 days earlier; the incubation period for viral gastroenteritis is typically 2-5 days.
Those comments answer questions 1-3.
4) The duo test is marketed and available nationwide. Not all clinics offer it routinely, but any doctor or clinic can request it through such national labs like Quest or LabCorp (which have local labs in almost all cities and towns).
5) Overview: It is very unlikely your symptoms are ARS. Since you're concerned, you should be tested; most people in your situation need more than verbal reassurance, and you can expect an HIV test to be negative. As you may know, the duo test is 100% reliable any time 4 weeks or more after exposure.
Best wishes-- HHH, MD
Thank you so much for the quick reply Doc - much appreciated. I know, condoms, condoms, always. I did make the attempt, but drunkenness proved to create a lack of coordination – and thinking. I’ve been through this before; I’m so disappointed I’ve put myself in the situation again.
But thank you again for your prompt reply.