What can this be?

Are you alternating ibuprofen and acetaminophen every 4 hours? If not start doing that, it’ll break the fever. And make sure you’re drinking tons of fluids and drinks with electrolytes!

Definitely Covid. Test again later today or tomorrow

Make sure you drink water. To help your fever you should be putting a cold and hot packs on your wrist ,head ,ankles an neck. you should pretty much be switching between cold and hot packs every 20 minutes. One thing that actually helped me break my fever after day two was taking a cold / hot shower switching between cold and hot every 10 minutes for 30 minutes got out did it again the night . 2 hours exactly at 1:00 am in the morning the next day my fever finally broke. Also if you have a child in the home and they go to school they could have brought that home. my doctor called my fever last year was a school fever He said he mostly sees the type of fever in kids in schoolm

Any dehydration, urinary symptoms, sore throat etc? It can be a sign of infection, or, sometimes fever can be your bodys way of fighting off a virus before other symptoms appear, which is a good thing. If it's the latter, it should go away in a day or 2. If it persists or you get signs of infection, time to be seen.