Well, let me start off saying "Uhh..that was interesting. Actually was better than a few Harry Potter reads". Do you write porn stories by any chances ? ..LOL !
Okay, sorry about the silly jokes, let's figure out what's wrong here !
Look, It's very unlikely that you might have contracted the virus from such a breif exposure (assuming she was HIV
the virus is high up there in the cervix and it seems difficult that you might have reached high up there in matter of 20 secs. You are freaking out for no reason, your own assumptions ( that your partner was HIV
positive) is screwing up your thought process. Yes, you should test since you went right inside her unprotected, get tested at the 6th week for an indicative result and back it up with a final one at the 12th week (It's highly unlikely for a 6 week negative to change ahead).
ARS, the nature of the symptoms that you described here don't match the ARS pattern. On the contrary it clearly seems to be an anxiety derivative symptoms.