Glad to hear you at least have a different doctor-- maybe this one will take concerns such as that a little more seriously?!
As a side note, I was thinking today... is it possible he has a food allergy and it's triggering something internally that is making him run a fever every day (like dairy products or something else he's had a lot of days for the last few months)? When I was little I got ear infections every 4 weeks (basically just enough time for the antibiotics to wear off again) until they figured out I was allergic to various things... I think it was milk, eggs, and chocolate, lol, and then the infections went away. Now I'm allergic to yellow food colouring, but don't have a noticeable reaction unless you check my urine (yay for urinalysis when you're pregnant, lol) and then I have so much protein spilling that it basically indicates kidney failure levels and everyone panics.

My dr. says that what is most likely happening is my kidneys become inflamed and stop working the way they're supposed to until the colourant clears my body. Anyway, I know fevers aren't caused by allergies but they can be a sign of symptoms you can't see, so just a thought I thought I'd throw out there...