Worried mama here

My toddler had a high fever yesterday, we gave her Advil and it went away, then it stayed away all day today so I thought she was better. But around 7pm tonight her fever spiked back up again and her breathing got a little faster. She still isn’t acting sick tho. I’m so confused as to what’s causing this. I’m hoping her fever goes away again and stays away for good. I feel like my child is always sick and it’s exhausting. The anxiety I get when she’s sick is insane. I literally can’t function.