I checked the boxes someone else can claim me and some else will claim me and my parents tax return was rejected because it said I claimed myself

Your will need to amend your return and not claim yourself and your parents will need to print and gile their return.  Your social security number is in the database now as claiming yourself, so even if that is a mistake, the only thing that can be done is for both returns to be mailed. Or your parents could take you off of their return and file without claiming you.

It may not have been you ... someone else either accidentally or on purpose put your SS# thru the IRS system and all your parent's can do is mail in the return to continue to claim you.   Another option is to remove you and efile the return then later amend the return to put you back on and mail in the 1040X.

I highly suggest you go online with the IRS and get set up with an IP PIN for use next year so that this cannot happen again ...  https://www.irs.gov/identity-theft-fraud-scams/get-an-identity-protection-pin