Temperature reading

My oura ring is connected to my Natural Cycles app, so I am able to see my temperature readings. I’ve been feeling under the weather, have gotten the “elevated body temperature” notification for the last few days (which is not a shock given how I feel), and my NC app says today my body read over 100 degrees F last night. I took my temperature with a regular thermometer this morning though and it’s normal, in the 98s (odd given how I’m feeling). Does anyone understand how these measurements could be so different? I also tested on two separate thermometers to ensure one wasn’t broken.