A few hours ago I visited a high end ($300) Asian prostitute. It was her first day on the job and we had intense chemistry that resulted in an insanely careless act: I engaged in unprotected vaginal sex with her for 10-12 minutes and ejaculated inside her. she said she had never done this before. Upon a brief visual inspection she seemed extremely clean and took care of herself (no weird sores or odors)

I was tested a few months ago the results were totally clear. But this episode has got me immediately concerned.

Should I check into an ER for PEP??

Welcome back to ur Forum.  I'll be glad to comment.  You do not mention where the encounter you describe took place but here in North America and Western Europe few commercial sex workers (CSWs) have HIV.  This statement is even more true among CSWs who charge higher prices.  Further, in the unlikely event that she had HIV, even then your risk for HIV from a single unprotected vaginal sex episode would be on average less than 1 infection per 2000 encounters.  Based on these data, personally I would not seek PEP which is expensive and has side effects but again this is a personal decision and should you feel strongly that you want PrEP, I'm sure you could find someone who would prescribe it for you. 

I would however suggest that an a couple of days, it would be best to get a urine test for the most common STIs, chlamydia and gonorrhea. 

I hope this perspective is helpful to you.  Please feel free to use your up to two follow-up questions if you have any concerns or further questions.  EWH

IF I took it, would it be a case of “better safe than sorry”? It seems like the stakes are so high and obviously I am concerned that I could never remedy this mistake, were I to become hiv positive,  if I do not take action soon.

There are multiple side effects to PrEP but nausea and vomiting are the most common problems.

FYI, while I would not take PrEP if I were you, if you choose to take it, sooner is better.  PrEP is ineffective when started more than 72 hours after exposure.  EWH

I will take your advice and skip it. Given what you know how confident are you that my hiv test will be negative?

I would estimate your risk for HIV as being less than 1 in a 2 million.  EWH