Ex’s failure to pay has left me behind on bills

I split from my husband and he about 3hrs away. He gets the kids every second weekend and I have to drive to a half way point. He has changed the weekends may times and has left me behind on may of the bills and I’ve had to borrow money just to get the kids to the half way point, my question is should he be paying petrol money as I can’t keep borrowing money anymore?

There is a lot more going on but this is beating me down. I don’t get all of my centrelink money as child support has me down as working when I had to quit when he left as I was a shift worker.

It’s gotten so bad the I can’t even run the car. I live in Canberra where the rent is very high I pay $980 a fortnight is there any way to get help for these money issues?