数日{すうじつ}から1カ月の間for the last few days of the month: その月の最後{さいご}の数日間{すうじつ かん}suffer from period pains for a few days every month: 毎月数日間生理痛{まいつき すうじつ かん せいりつう}に苦しむfew days: few days数日すうじつ