A Catholic Dilemma

An issue of much debate and discussion today in our American society is the issue of life. More specifically, when the start of life happens. What are the conditions or requirements that characterizes the person as living? This debate has evolved from abortion to stem cell research. As many Christians and Catholics know, the right of life should be always regarded as something special and sacred, a miracle from God. People who support abortion apparently want to deem it okay to end someone's life. This is wrong because we are hurting someone, an act of murder. More importantly, in my opinion, by ending a person's life we are playing God, which we is heresy and sinful. God is the only one who can determine life and death because he can actually create life. If a life is created, then it shall be allowed to life. We are not allowed to tamper with God's works (which should lead us to disapprove of the death penalty and of destroying the environment, but this is the the subject for another time).
The issue of stem cell research makes the issue more complicated and leads us to hazy grey areas. Before our time, life was always thought of as starting in the mother's womb at conception where the sperm and egg came together to form the fetus. As time has passed by and science has increased technological advances, we are now able to create embryos outside the body and then implant it into the womb. The curious procedure that many Christians blindy go through when they want to get pregnant with the help of science through in vitro fertilization is that this process takes harvest several eggs from the mother's womb and fertilizes them with the father's sperm. A couple are implanted into the mother (because by chance only one or two actaully grow to be embryos and the other ones die off), and the others are frozen away just in case the mother does not become pregnant. This process creates a surplus of human embryos that science wants to use in stem cell research to help find cures. The problem that morally jumps out at me is: Is it right to destroy a life to help cure many other lives? A deeper question we must ask ourselves is when does life start? Does it still start with with the sperm and the egg coming together to form embryos? Or does the embryo have to be in the mother's womb to be considered a womb? In my opinion, life starts when the embryo is implanted in the womb because if that implantation does not start, then the embryo will die off. Without that critical process, then a human being cannot be formed from an embryo. However, does that mean that frozen embryos from in vitro fertilization clinics can be determined to be non-human? Clearly not for obvious reasons because these embryos if implanted would have the potential to become human. If that is the case, what are we going to do with all these frozen embryos in those clinics? I am pretty sure not every Christian/Catholic woman will agree to implant these embryos to help deliver children. So what then?
Stem cell research seems to be a viable option because research on them could find cures for diseases such as diabetes because killing off a few embryos would save countless numbers of human lives. It is like sacrificing one's life in a dangerous situation to save a life of a friend. However, we are not ones to determine if a life is ended or spared. To reiterate, God is the only one that can do this, but this leads us to the main question, when does life start? Is it when embryos are formed or when the embryo is implanted? People of religious authority have said that stem cell research is immoral and evil. However, they do not have clear and concise arguments of why it is not. I am a scientist and a Catholic, a person stuck in between. I will need a peron in the clergy with scientific background to explain this dilemma to me.