Why is my dog misbehaving?

shes 8 months old and to be honest she was doing very well with her training up until bout 3 weeks ago...? shes now started peeing on the floor instead of going to the door like she usualy does. she wont come to us when we call her, if she does something wrong and we tell her off and put her on her bed, normaly she wont do it again, atleast for a while lol but recently she will go to her bed, then come back and do it again straight away. also she has started biting the back of my legs which she used to do when she was little but she stopped. She has enough excersice and loads of toys/ bones and gets alot of attention. why has she started misbehaving? She is a Beacoun cross Doberman. We have a baby due to arrive in 10 weeks so i need some ideas to help calm her down again? lol