A lot of women who suffer from period pain every month rely on prescription drugs.
There are a lot of women who rely on prescription drugs when they have monthly menstrual pain.
この場合、次のような言い方ができますよ。
ーA lot of women who suffer from period pain every month rely on prescription drugs.
「毎月生理痛に悩まされる多くの女性は、処方薬に頼ります」
to suffer from period pain every month で「毎月生理痛に苦しむ・悩む」
ーThere are a lot of women who rely on prescription drugs when they have monthly menstrual pain.
「毎月の生理痛があると処方薬に頼る女性がたくさんいる」
to have monthly menstrual pain で「毎月の生理痛がある」
ご参考まで！
カナダ 
