I don't seem to be speaking English very well today.
I'm having trouble speaking English today.
この場合、次のように言うと良いでしょう。
ーI don't seem to be speaking English very well today.
「今日はあまり英語をうまく話せないようだ」
don't seem to be speaking English very well で「あまり上手に英語を話せないようだ」
ーI'm having trouble speaking English today.
「今日は英語を話すのに手こずる」
to have trouble ~ing で「〜するのに手こずる・苦労する・困る」
ご参考まで!