I had a high fever for quite a while, but it's back to normal now.
My temperature was high for a few days, but it finally came down last night.
この場合、次のような言い方ができますよ。
ーI had a high fever for quite a while, but it's back to normal now.
「しばらく高熱がありましたが、今は平熱に戻りました」
to have a high fever で「高熱がある」
it's back to normal で「正常に戻る」＝この場合だと「平熱に戻る」
ーMy temperature was high for a few days, but it finally came down last night.
「数日熱が高かったけど、昨夜やっと下がりました」
下がったということは平熱になったとも言えます。
ご参考まで！
カナダ 
