Ugh! (Ranting)

Well I really need to express myself... Sorry if its a bit long. Well I have a stepson that lives with us he is 4 now and he is completely disrespectful. He talks back, he throws tantrums, he screams at the top of his lungs when he doesn't get his way, he acts up as soon as his dad comes around and don't listen to anything I say. Of course he has a mom but he lives with us and I take care of him whereas his mother only gets him every now and then. But my husband says nothing about him being the way he is in fact he makes up excuses for his behavior and gets upset when I try to discipline him. Tbh I'm sick of this shit. Its really hard trying to raise a child that does not listen to you. And on top of that having to argue with his father every time you try to discipline him and being pregnant. He treats him like a baby and it will be 2 babies under him when my little boy arrives. My nerves are really shot to hell already because I'm always tired and I have a 11 month old to deal with. Sometimes I really wanna just be like well just keep your own child or send him to his mother because I'm not going to continue to put up with a child that does not listen and I can't discipline... Before you say talk to your spouse about it I've already tries that numerous times and it gets me nowhere.