When a baby is born, it becomes a human being? Do you not realize that as long as the baby is still connected to the umbilical cord, he/she is not breathing on his/her own? According to your standard, you could cut that baby to pieces with a saw and not be killing a human being. Also, there are many people we consider to be human beings who are totally dependent on machines and other people for nourishment, waste removal and oxygen. Sorry, you need a new standard, because your arbitrary one isn't consistent.
You keep repeating the nonsense that an unborn human is not a human being. Check the definitions of "human being" and tell us where you find a distinction between born and unborn. They're all human beings. See, your fallacy lies in the meaning of words that you are making up to justify your religious beliefs. "Human being" means something different from "person". Human being is a biological term, a scientific one that does not change just because you want to devalue the lives of some group. Remember that this was tried with African slaves, partially to justify treating them like animals. Person is a legal term and that is what you should be going for. In a sane world, you would be arguing that a human baby becomes a person at birth, with recognized rights and freedoms (if they are born in the US). Your dogma, however, won't let you admit that an unborn human is a human being, because that would weaken your argument that an unborn child is not even a human being, is worthless and thus can be violently destroyed on a whim with no repercussions or consequences.