Child support

I went and signed my children’s father up on child support may of 2019, and they say they couldn’t find him. I gave them his address, ss number where he worked, everything. They say they couldn’t find him. Well after the pandemic he says he quit his job and is using unemployment and living not far from me with his new girlfriend (she isn’t a problem at all, i love her!) I don’t know rather to believe it or not. but he will not help me AT ALL. But expects me to let him get the kids anytime he pleases. If anyone has any advice pls help. I’m so tired of struggling while he can do what he wants and spend 400 on a tire rim, but can’t send me 100. I have our kids the majority of the time. He usually doesn’t get them but maybe once or twice a month but recently demanding them more.