Fever (>38,3°C rectal) is an increase of body temperature due to a change of its set-point. This new set-point is tolerable. It's different from hyperthermia (>41,2°C) which is based on a failed thermoregulation. Getting a fever brings advantages in order to fight off microbes more efficiently -while hyperthermia does non of the sort (and of course the cause is different). Anyway in the case of fever, your body tries to stay on the same level as the new set-point. In order to do that peripheral blood flow/production of sweat is reduced/ (so you don't lose heat) and in the end you get cold hands/feet/nose. If that is not enough you start to shiver so your muscle start to produce heat as well.
This concludes that keeping your body as warm as possible is to your adavantage. If it is too much, your body will get rid of excess heat by sweating (if your hydrated enough and don't suffer from a disease which messes with these regulation systems).
I guess that people think like you explained is, because people tend to take an approach of reducing the fever as fast as possible. This doen't have to be necessary though^^ hopefully that explained it.
The phase in fever when you're feeling chilly is the part where the infection has already spread and messed up the hypothalamic thermostat to a level higher than the average body temp. So, the body works to raise the temperature of the rest of the body to reach that "high" set temp in the hypothalamus. (Scientifically called thermal regulation)
So the person who's sick is actually burning (when you take the temp) but shaking (shaking/trembling are one of the mechanisms to raise body temp) and feeling chilly because their hypothalamic temp is still much higher than the body temp.
Once this process gets under control (takes up to hours) the body has already started fighting off the infection and the hypothalamic thermostat temp drops back to normal. But the body still has high temp so temp lowering mechanisms come in play and sweating starts (which is the biggest and most effective way to remove body heat). The more you sweat, the faster your temperature drops back to normal. (So that's why in my culture and other Asian cultures, we sweat the fever away...so it's not a myth xD)
Scientifically, this term is called a "flush" and the most awaited part (for doctors) of treating an infection because it's an indication that the body's got this under control and there's no need for medical intervention.
(If the temp doesn't drop in a day or so, they have to ice pack or dip the person in cold water to manually cool him down and stop the overheating)
So if you have sex and sweat, that will make your temperature go down but in no way completely cute your fever cause gotta wait till the immune system completely fights it off. (Usually takes a week or so)
God, I actually typed such a long message.
I'll be glad to link to the thermal regulation chapter in my physiology book if you're interested xD
I made it as simple as I can.
Can someone tell me why in manga or anime (mostly where I see this) that when someone gets a fever they make them be in the blankets (like big think hot blankets) and put them in extra layers of clothes?? I thought when someone gets a fever they are not allowed to be in things that will make them hotter because they can overheat and get more sick then they already are. I feel kinda sorta stupid for asking this, but someone please help educate me ٩(๑❛ᴗ❛๑)۶