Couldnt care less

Could care less makes NO SENSE? if you could care less then its obviously not that big of a problem, as theres more things that would bother you lol

'I couldn't care less' is definitely correct grammatically and correct for the way it is used.
Although, I could care less could be a full sentence too.
If someone asked 'are you not really bothered?'
You could reply 'I could care less,' meaning you do care slightly...

Did you mean 'precocious'?

It is a term for children, but it's not necessarily an insult. Although, I would use it more in an insulting manner. I'd be more likely to say 'precocious little brat!' But really it just means that they're old before their time. I think people tend to use it more about kids who are a bit too smart-mouthed for their own good. lol

Ive often heard it used for teens who are sexually active early too :L

I've never heard that. I think a lot of these words are used in different ways depending on the area you live.