I went to file my taxes for me and my kid and 3 days later I get a call from h and are saying some one filed ME!! What am I supposed to do? How can I find out WHO?

If you think that you are the one who can claim the dependent, then file your tax return and claim the dependent. It you are unable to efile, then send paper return. IRS will then contact both of your and figure out who must amend the tax return and pay the tax due with interest and penalty.

Child of divorced, separated or unmarried parents:
Only the custodial parent can claim the child. It does not count who is paying child support. The custodial parent is the parent with whom the child lived for the longer period based on the nights spent. The other parent is the non-custodial parent.

Non-custodial parent can claim the child only if the custodial parent signs a release Form 8332 or there is a court order meeting the IRS requirement. Your U.S. Tax Return: Child of separated or divorced parents (http://taxipay.blogspot.com/2008/03/child-of-separated-or-divorced-parents.html)