You're still talking about the same thing you were talking about last year.
You're still going on about the same thing you were talking about the last time we spoke.
この場合、次のように言うと良いですよ。
ーYou're still talking about the same thing you were talking about last year.
「君は去年話していたことを同じことをまだ話しているね」
to talk about the same thing で「同じことを話す」
ーYou're still going on about the same thing you were talking about the last time we spoke.
「君はこないだ話した時と同じことをまだ話しているね」
to go on about ... で「…について話し続ける」
ご参考まで！
カナダ 
