So on Tuesday evening my son's head felt hot so we took his rectal temperature before bedtime, and it was 101.8°. The only thing that was strange about him that day was he seemed a little less interested than usual in breastfeeding and solid food eating, so we were really surprised the temperature was so high.

We took his temperature again three hours later and it was down to 99.6° so we figured we were heading back to normal.

Wednesday morning, 99.4°, that night, 100.1°, Thursday morning 99.5°, tonight 100.3°

His behavior and eating normalized on Wednesday and today (Thursday), and he's actually been more interested in breastfeeding, presumably to get those extra fluids. He's still sleeping pretty normally, and his activity levels are the same as always. Poops and wet diapers normal too.

What gives? Should I be worried? He is teething, which I've read can only cause small elevations in temperature, but not enough to be considered a "fever" (obviously 101.8° is a fever but even 100.3° is below the 100.4° threshold for official fever), but does it really go on for this long?