If i accidentally claimed myself as a dependent, how can i change that on my taxes so that my mother can still claim me on her taxes?

Did you already e-file?   And now your mom's e-file is bring rejected?

I SHOULD HAVE SAID I COULD BE CLAIMED AS A DEPENDENT

Did you say you could not be claimed as someone else’s dependent, but it turns out your parent(s) can claim you?  Now your parents’ return is being rejected when they e-file, or it will be rejected.  That means your parents must print, sign, and mail their return.  They can still claim you as a dependent, but they cannot e-file now.  Not even if they wait for you to amend, so they should not wait for you to do that.   The only way for a parent to file after a dependent has made this mistake is to file by mail.

Your part in fixing this is to wait until your return has been fully processed and you have received you refund.  THEN you need to file an amended return, called a 1040X, to change the way you answered that question in My  Info about whether you can be claimed as someone else’s dependent. 

If it is any comfort, you (and your parents) are among many young tax filers who make this mistake.  We will be seeing plenty of posts just like yours.   And posts from the parents whose e-files were rejected....