I'm not sure how to understand/translate the phrase 「じゃ無いんじゃないかって」
それはあんまり良いことじゃ無いんじゃないかって
For more context, previous sentences translated to:
You always had those (headphones) on when you were walking right? Even during the times you didn't use them, they were definitely in your bag.
I understand that it's talking about how that something is not very good?
But I'm thrown off by that phrase