There was someone else I was interested in so I couldn't give him a straightforward answer (when he told me he liked me).
I was interested in another guy so I couldn't give him a straight answer
「他に気になってる男性がいたから前向きな返事ができなかった」＝ There was someone else I was interested in so I couldn't give him a straightforward answer (when he told me he liked me). / I was interested in another guy so I couldn't give him a straight answer
ボキャブラリー
someone else, another guy ＝ 他の人（男性）
interested in ＝ 気になる（人）
couldn't ＝ できなかった
give a straight(forward) answer ＝ 前向きな返事をする
when he told me he liked me ＝ 彼が告白した時
イギリス 
