Deductions & credits

We legally divorced 4 years ago. I thought he would be categorized as other dependent for me because I paid more than 90% of the cost of maintaining a qualifying household, paying all expenses, including rent, utilities, repairs, and groceries. Can I claim him as my dependent, not filing as a head of household? I filed my return, then should I amend my return removing him from my dependent, or the IRS would adjust it? What should I do?