Really? You could? Because that means you care at least somewhat right now. Otherwise, it wouldn't be possible for you to care any less than you currently do.
Perhaps what you meant to say was:
This means you care so little that it's not even possible for you to care less about it. You don't care at all, not one iota.
Oh, how this phrase pains me! It pains me almost as much as seeing the wrong form of they're/their/there. Or apostrophes on a plural non-possessive word.
Please, make the world a better place. The phrase is "couldn't care less". And if you use it wrong, I'm going to send angry neighbor's dog to eat your face. (See how I use apostrophes and your correctly there? I'm sure you couldn't care less.)