「あれから考えたんだけど」は
I've been thinking about it since then
I've been giving it some thought
のように言えます。
例:
I've been thinking about it since then. Personally, I would like to learn about .... What do you think?
「あれから考えたんだけど、個人的には…について学びたいと思います。どう思いますか?」
ご参考まで!
Ever since that time, I've been giving it quite some thought
I've been thinking about it since that time
ご質問ありがとうございます。
「[あれから](https://eikaiwa.dmm.com/uknow/questions/24932/)考えたんだけど」は英語で「Ever since that time, I've been giving it quite some thought」と言えます。
また、別の簡単な言い方で 「I've been thinking about it since that time」でも言えます。
ご参考になれば幸いです。