At my whits end..

My 6 year old step son has ADHD and behavioral issues. He moved in with us in January after his mother decided to up and leave and go to Florida.

So I understand he's going through a lot, and for a while he was doing pretty good.

For the past month he's been pooping his pants 3/4 times a week, acting out horribly and getting an attitude over everything he doesn't like. He has absolutely no independence, my 2 year old has more.. And whines and balls his eyes out every time he gets in trouble, and I'm not kidding.

I'm 34 weeks pregnant and am honestly at my whits end with him, I have no idea what to do. Nothing seems to be helping. I take his Xbox away, but honestly he's not my child and his mother is crazy so I try not to discipline him a whole lot, I usually leave that up to his dad.

Is there anything anyone recommends doing to help? Or programs to get him into to help? I'm seriously drawing a huge blank on what to do..