The relevant Amendments of the Constitution to Abortion:
9th:
The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.
10th:
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
It's an issue of state rights vs. individual rights. #9 says that the people retain rights that are not specifically prohibited by the Constitution. #10 says that anything not mentioned in the Constitution is retained by states, or the people. So what you are arguing is if the state has a right to interfere with a woman's body, against her will. The people of OK obviously decided it was within the states rights to do so, and gave up some of their freedom to allow it.
I think it is similar to the "right to die" position, in that terminally ill patients have a right to not continue treatment. To me, it's a personal issue, and one that is most likely not reached lightly. I do not believe religious grounds should be permitted in the discussion, simply because this a country where we are free to express any religion we choose. What if my religion condemns a family that brings a child into the world that it cannot support? Or one addicted to crack? Or one that will live a life of terrible suffering due to a severe genetic problem?
The problem with abortion is that people try to make it a black and white issue, but it's not (like a lot of things). There are many shades of gray. I'd agree that using abortion as a form of birth control is outrageous. I'd also say forcing a women who was raped by her father (or anyone) to have a child is equally outrageous. Some say only if the mother's life is in danger, but that's flawed because pregnancy is inherently life-threatening. Think of all the women who have died giving birth.
I don't think you can take the position of "no abortions except in cases of rape/incest" because then a woman who wanted an abortion would have to say she was raped. Rape is horrifically under reported, usually about 5% of rapes actually get reported to the police. Many women who ARE raped (as defined as unwanted oral/vaginal/anal penetration) do not consider themselves to be raped. My senior project in college is in Sexual Victimization among women, and I can tell you that all the research points to about 50% of women experiencing some type of unwanted sexual contact (fondling, consensual but unwanted sex (coercion), attempted rape, completed rape) during their lifetime, but few will say they were actually "raped" even if they will admit to experiences that are legally defined as rape. They do not want the label of being a rape victim, or they blame themselves, or they worry what others will say. It's a very dicey issue, and learning about the psychology of rape has really changed my view on abortion.
I hate abortion, but I am unwilling, based on my education and personal beliefs, to impose my view on other people. To those who use religion as a cover, I will remind you that it is not our job to condemn people. "Let he who is not a sinner cast the first stone." If there is a God, and I think there is, then it is solely within God's responsibility to determine whether or not what the person did during life deserves to be punished. Like it or not, people are FREE to have different viewpoints in this country. Learn to accept it, and live your own life, rather than worrying about what other people choose to do with theirs.