Unexplained fevers

Age: 6

Sex: Female

Weight:36lbs

Symptoms: Fever on and off since Saturday with not other symptoms other than looking sleepy

My daughter developed a fever Saturday night, its been lingering since then and it is now Thursday morning, She is acting totally normal other than when the fever gets high 39.6, then she complains of feeling sick but once her Advil kicks in she's back to bouncing off the walls and talking and acting completely normal. My husband seems to think that because she is acting normal there really isn't anything to worry about, but of course I'm worrying, I'm losing sleep thinking worst case scenarios in my head like what if its strep, what if its a kidney infection, what if its something terrible. Yesterday she went the entire day pretty much fever free, that lasted until about 1:00Am where her fever spiked and she started tossing and turning in bed so I gave her some more Advil. This morning she woke up at 7 feeling slightly warm but the thermometer only read 36.9.

A couple of weeks ago she was urinating quite frequently but it was only when she was at school and at a couple events we went to other than that she was totally fine at home, she suffers from anxiety and constipation so I figured the frequent urination was either an anxiety response considering it was only happening when she was away from home and actually happens quite often with her or because her bowel was full and pressing on her bladder which is what her pediatrician told us can happen from time to time. But now I am terrified it may have been a UTI and maybe the fever was a delayed response as she has not had a bout of the frequent urination in about 2 weeks.

I'm just looking for a little input on this. a little breakdown of what were dealing with, Fevers tend to spike in the evening or at night, she's acting normal, but when fever spikes she gets chills and nausea, Advil brings her right back to normal, her appetite is off but she is drinking plenty of fluids. And she's a tiny bit pale and her face looks sleepy. Also the time between fevers seems to be getting longer which I hope is a good sign.