Step son

Do I have the right to be mad at my baby daddy's 6 year old son when baby daddy leaves to do whatever the fuck hew does and leave me by myself with my 7month old daughter and his bad 6 year old son. His son gets so mad and starts throwing things and screaming and pushing things over in his room and I have to take care of my 7 month old with her needs and it just so stressful dealing with his tantrums and all I can do is send him to his room to have him be more mad stomping screaming kicking and throwing things... I'm about to lose it over here being left alone with a out of control kid and juggling a baby. So do I have the right to be mad when I'm stressed from dealing with the two kiddos