Both my kids were like this with the recent bugs they've had. DS has another temp today so looks like we're on round 2 yay. It is scary, but just try and keep the temp down with the nurofen/panadol combination if you can. Also don't be afraid to get the tepid flannel out. When DS got his tonsil infection I sat with him most of the night cooling his head down purely because we didn't have the combo on hand and it was 2 am when the fever started. I was tired the next day but it kept his temp around 38 till it broke in the morning. And he was fine, he slept through the night.

ETA: But also if you are worried DEF go see a Dr. If DS's temp didn't stay down I would have went for sure.