I didn’t tell you on purpose (Because I thought you would worry)
I deliberately didn’t tell you. (because I thought you would worry)
Deliberately/ on purpose = あえて、わざと
Tell you = あなたにいう
Because i thought you would worry = あなたが気にすると思った
On purpose の反対語は “by accident”か”by mistake”
例 “I told her by accident.”
彼女についつい言っちゃった
アメリカ合衆国 
日本 
