39.9c temperature 🤒

Hello so I just wondering if any one else has experienced this with there little one my 3year old broke out with a temperature of 39.9 and even after calpol it only brought it down to 38.8 I still wasn’t happy with that so I rang 111 and had phone call appointment with a doctor who suggested alternating calpol and ibruphen 3 hourly 3 of each every 24 hours and said if the temp hasn’t gone down in 5 days to ring the doctors however we are on day 3 now and her temp is constantly going from 39.9 all the way down to 35.5 and up again she shows no symptoms other than this crazy temp I honestly don’t know what else to do her doctors surgery isn’t seeing patients face to face due to covid so they are no help and like I said she’s showing no other symptoms so the doctor that I spoke to doesn’t seem to know what it could be and I’d just like to add she has had a 2 covid tests that have come back negative so it’s not covid either please if any one has any advice on what it could be or where to go from here that would be great tia x