Wow, I didn't realize people had replied.
My friend's a social worker and works with a psychiatrist, so she asked him about this. He said that anxiety shouldn't cause a fever but a fever will likely cause anxiety. My gastroenterologist, however, is the one saying I'm having "modified panic attacks" and did tell me that anxiety could cause a fever.
So I don't know. It could be that I was just fighting off a sinus infection or something. I've since read on these internets that body temperature varies "up to a degree" throughout the day. The other day I thought I had a mild fever and the thermometer registered 99.6 degrees. The next morning I took it out of curiosity and it came up at 96.3 degrees. This was before I ate or drank anything at all. I do smoke and that plus a sinus headache or a random allergy could've made me think I was feverish that night, I suppose. Apparently you're not supposed to smoke for a while before you take your temperature.
E-Girl, these fevers were recent phenomena that happened only a couple of times as far as I could tell. If my GI is right, then I've been suffering panic attacks for about two years. I don't know whether or not I've had blood work specifically for a tick-borne infection, but I have had a LOT of blood work done over the last couple years. I live in a very urban environment and doubt I've been exposed to ticks, but thanks for the suggestion.
Thanks for the responses. Still inconclusive, I guess, but maybe someone will search for this someday and the information will help them out.