My sons mother filed him as a dependent but its my year. So she filed an amended return on feb 27. How long until my taxes stop getting rejected?

There's no set time.  In a normal year, it can take 6-8 weeks before the IRS processes an amended return.  This year, with the additional demands for distributing stimulus checks, it could take months.  Your best bet is to print and file your return by mail.

Once a ssn has been used it won't be released to efile again.    You have to print and mail your return even if they amend.