I feel like my English conversation skill has not been improving much, so I'm a bit worried about that.
ご質問ありがとうございます。
下記の言い方ではいかがでしょうか。
I feel like my English conversation skill has not been improving much, so I'm a bit worried about that.
--- to feel like ... = ~のように感じる
--- to improve = よくなる
--- a bit worried about ... = ちょっと心配です
ご参考にしていただければ幸いです。