I’m Jewish. Even though I don’t believe that Jesus of Nazareth is the Messiah, I don’t believe that Christianity is a lie.
As the Orthodox Rabbinic Statement on Christianity stated:
Both Jews and Christians have a common covenantal mission to perfect the world under the sovereignty of the Almighty…We Jews and Christians have more in common than what divides us: the ethical monotheism of Abraham; the relationship with the One Creator of Heaven and Earth, Who loves and cares for all of us; Jewish Sacred Scriptures; a belief in a binding tradition; and the values of life, family, compassionate righteousness, justice, inalienable freedom, universal love and ultimate world peace.
The things we share in common that I as a Jew love dearly are not worthless nor empty like the lies of the world. Thus you cannot say that the Christianity you practice “is all a lie.” It is not. We both share in a most marvelous, priceless heritage, one of truth and enlightenment.
Christians are not alone in the world. The beautiful, sacred truths found in the Roman Catholic Church are an inheritance from the Jewish Patriarchs still shared with among the Children of Israel. We are together in drinking truths from the richness that flows down from Zion.
You may wish to speak with your parish priest about your feelings or another cherished spiritual counselor that you can trust. You should also consider joining a basics class in your faith as a review or refresher (or perhaps find some people to go over the adult catechism in a discussion circle with you). These steps might help you to see the validity of what you have been taught and bring new light to the faith which you belong to.