If a guy cums then fingers a girl can she get pregnant even if she's not ovulating but is taking pre natal's and nursing a baby ?

No egg = no baby: Regardless of what else is going on, a woman cannot get pregnant if she is not ovulating (no egg = no baby). The problem is, how does a woman know she is not ovulating? If she has her ovaries and is not post-menopausal, she may ovulate at some time... which means she has an egg at some time (egg = potential baby). If she ovulates at some time, she should use a form of birth control all the time.