I have dd 2.1 and dd 5 weeks. Oldest dd is coping really well with new baby except when tired, hungry etc. Twice now I have reacted physically and instinctively to older dd hurting little dd (she doesn't know she is really hurting her - or is only doing it to wind me up). Once I tapped her hard on the shoulder but today I picked her up and shook her (one shake) because she was kicking the baby. It was quite gentle (the shake), but scared the hell out of both of us. It was completely instinctive and I don't think I could have stopped myself. Now am terrified I will actually hurt her without being able to stop if she does something to the baby. I have never raised a hand to anyone in my life until this and am finding it really frightening. Please advise.