@Lagatita85
Are you legally divorced? If so, it would be nearly impossible for your ex to legally claim you as a dependent. If you are still legally married, he may have filed you on a joint return.
Either way, as VolvoGirl said, you can no longer e-file. The only way to resolve this is for you to file you own tax return, on paper, in the snail mail. You claim your kids and everything else you're entitled to.
If you are still legally married, reply back for more details on how to file. You cannot use Single Filing status. You MIGHT be able to use Head of Household but may have to file as Married Filing Separately (MFS). You cannot claim EIC if you file MFS
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If someone else claimed you, and your kids, as dependents, inappropriately, and if they file first, your return will be rejected if e-filed. You would then need to file a return on paper, claiming yourself, if appropriate. The IRS will process your return and send you your refund, in the normal time. Shortly (up to a year) thereafter, you’ll receive a letter from the IRS, stating that your exemption was claimed on another return. It will tell you that if you made a mistake to file an amended return and if you didn't make a mistake to do nothing. The other party will get the same letter you did. If one of you doesn't file an amended return, unclaiming the exemption, the next letter, from the IRS, will require you to provide proof. Be sure to reply in a timely manner.
Winner gets the tax benefits; loser gets to pay the IRS back with penalties and interest
