「自分で言っといて気付かなかった」は
I forgot that I told you ...
を使って言えるかと思います。
質問者さんのシチュエーションだと下の例文のように言うこともできます。
例：
I just realized I told you not to send it by EMS at first, but then I told you it's ok to send it by EMS. What was I thinking?
「EMSで送らないでって言ったのに、EMSで大丈夫だよって言ってたね。私ったら何言ってるんだろう。」
ご参考まで！
I didn't realize it, although I had told myself so earlier.
"I didn't realize it"＝「私は気づかなかった」
"although I had told myself so earlier."＝「私は自分自身に以前、そのように言っていたのにも関わらず。」
Example in context:
"I had told myself that sending things by EMS is not an option now, but I forgot my own reminder, and told someone to send something by EMS."
カナダ 
アメリカ合衆国 
