Is it possible for a father to get custody of his two children in Indiana?

I have two little girls that my ex wife has current custody of. I pay 225 a week in child support and have never been late. Since the divorce, my ex wife hasnt had a place of her own, and has bounced around with family members, moving the kids with her, switching schools. In the last two years, she has moved residences 4 times. In the last 2 years, she was arrested for domestic battery, but plea bargined for a battery w/ injury charge. She just now started working(10 hrs) a week and lives with her mother (for now, until they have a falling out.) She drives them around in a 10 year old Kia Rio, that is unsafe and unreliable. I can provide them a stable home, with real food everynight (not fast food), thier own room, and give them a good stable life. Now my ex is taking me back to court for more child support (as she is going to vegas with freinds for a week next month). It upsets me that i see my kids going without, and he using the money for personal reasons, while she mooches off her family.... Any advice? Thanks