You were properly using a condom for birth control, right?

Literal

Contraception [topic-は] properly condom attached-was [explanatory-の] [agreement-よね]?

A direct, concerned question. 避妊 (contraception) is a medical term used casually here. ちゃんと (properly) emphasizes doing it correctly. ~てたのよね chains the casual contraction ~てた with the feminine のよね (explanatory + confirmation-seeking). The tone is worried but familiar.