That's good that you're planning on testing. That's the only way to know for sure, after all. Make sure you wait at least six weeks after the encounter before testing though.
After you take the test, you could always wait a few weeks more, then go to your doctor or a clinic to get a test from them just to be on the safe side.
You're right that people can get all kinds of crazy symptoms from stress. Many people who worry about HIV swear that they have all of the symptoms even though they don't have HIV, just like many girls who worry about pregnancy swear that they have all the symptoms even though they're not pregnant!