I don't think my English abilities are getting any better. It's just that you are better able to understand me these days.
この場合、次のような言い方ができますよ。
ーI don't think my English abilities are getting any better. It's just that you are better able to understand me these days.
「私の英語力が上達しているんじゃなくて、最近、あなたの私を理解する力が成長しているんだよ」
you are better able to understand me. で、「あなたが私の言いたいことを汲み取る能力が長けてきている」ことを言えます。
ご参考まで!