Ok i have a question to mothers who have lost there drive?

our baby is 7mths and we also have two year old ok i take care of the kids only thing she does is come home eat,and bathe she will,help me take the kids a bathe play with them for about 15 min and thats it i wash cook take kids to nursery pick them up and for seven mth when i try to touch her or ask about having she says shes tired or shes stressed out about her job is this normal after having a baby cause it wasnt like that with our first baby please help thinking about leaving