When our children have stomach bugs or colds, we seem to deal with it with no anxiety, but for some reason, when children have fevers, even the most relaxed parents can get worked up over it.
First of all, he is in pre-school. There will always be bugs going around...either one child or another has a runny nose or a cough, or a low-grade fever or an ear ache. It seems the cycle never ends at times. Often times, it's just a little something that makes its way through the system (both the school's and the child's *grin*).
Also, as I mentioned already, for some reason fevers strike fear into many parents. While it is definitely important to really tune into your child and be aware of what is going on, it can be helpful to remember *why* we have fevers in the first place. The body will produce a fever in order to stimulate the immune system to respond to some sort of disturbance (i.e. a virus). A fever is only one symptom, and it is a good sign that your child's immune system is *working*!
I think it is *really* important to look for other symptoms present. Some symptoms can be a bit more elusive than others. Vomitting or a runny nose or a rash are very tangible, but a headache can be more challenging to detect. Have you asked your son if any body parts hurt? If he has a hard time with this question, you can ask if his body parts feel good. Sometimes just switching the perspective can help clue them (and you) in to something that doesn't feel like it normally does.
I would recommend going to your library or nearest bookstore and checking out "Take Charge of Your Child's Health" by George Wootan, M.D., and Aviva Romm's "Naturally Healthy Babies and Children." Actually, I would highly recommend buying them. They are invaluable and indespensible. I believe if you get these two books and actually read them (not just when your child is sick), you will be more in tune with your child's health during both their well and sick times, as well as cut down on trepidation about whether or not to bring him in to the doctor, *and* cut down on doctor visits in general.
The more informed you are, the more you will be able to decipher more clearly when to just stay home and give your little one extra nourishment and nurturance while his body fights off whatever it encouners, and when it is imperative that he see a doctor. And the more confident you become, the more you will be able to trust your gut when, even though he may have a low fever or few symptoms, it tells you that something more serious is up. (Or, on the flip side, when he has a high fever with no other symptoms, but you *know* that what he really needs is rest).
I feel like this was rather vague, but I hope this helps in some way, and I wish you and your little boy health and happiness!