under the weather

Meaning: 体の具合が悪い、気分が悪い、二日酔いである

For Example:

‣ I have my English final today, but I'm feeling under the weather. So, I don't know I will fare on the test.

今日英語の期末テストやのに、体がえらいわ～。テストでちゃんとやれるか心配や。

‣ I ate so much at the buffet last night, now I'm a bit under the weather.

昨夜バイキングで食べ過ぎたけん、今しんどいが。

Synonym:

feeling sick, not in good shape