The chance she actually had HIV (extremely low) and the chance you caught it from 2 encounters with her if she actually was infected ( 1 in 1000-2000 exposures to a known positive person) addd up to be a miniscule risk, but nonetheless still there. Google "handsfield risk perspective" to calm yourself even more. He is an STD "expert".
Symptoms mean squat, and are almost always attributable to one of 10,000 everyday things. I have been here nearly 2 years, and I have seen countelss people come here with "every symptom in the book" and not seen one turn out positive.
Go for a 6 week test, that will be in the area of 99%+ accurate, meaning over 99% of people would have tested positive for antibodies had they actually been infected. Combine a negative test with the other 2 chances I listed above, and a 3 month test is a formality at that point