I'm so sorry you are suffering with these difficult thoughts and ideas. I'm wondering if what you are really suffering from though is post-partum (sp) depression? This happens to many women after giving birth and can be helped even if you are breast feeding. Please call your doctor and tell them what you are feeling and going through. You are not crazy, you are suffering an illness and you deserve to be treated and taken care of for your sake and that sake of your family.
You are in my prayers!