~ from email ~
This issue is common, and it might take some time before it is resolved. Gain a firm grasp of a coherently formulated system of Christian theology. If you are misinformed about the Christian faith, then naturally there would be oppressive questions. If there are indeed logical doubts, overcome them by praying about them and by studying biblical apologetics.
However, it appears that your problem is not mainly rational in nature. You would still doubt even if you perceive that the Christian faith is rationally perfect. This is because you are not perfectly rational even though the Christian faith is perfectly rational. Sin impedes rationality. Faith is not something that comes only by arguments, even though God often uses them to produce faith. Faith is a gift from God.
Jesus said, “But you do not believe, because you are not of My sheep. My sheep hear My voice, and I know them, and they follow Me; and I give eternal life to them, and they shall never perish; and no one shall snatch them out of My hand” (John 10:26–28). If one does not finally believe, it is not because the Christian faith is not rational, but he does not believe because he is one of the reprobates, chosen for damnation. Nevertheless, if you have persistent doubts, this does not necessarily indicate that you are one of the reprobates. It could be a struggling phase in spiritual growth. You must continue to pray for God to show you the truth, and to fill you with assurance.
Mark 9:24 says, “Immediately the boy’s father exclaimed, ‘I do believe; help me overcome my unbelief!'” You might be in a similar position – it is not that you have no faith, but you have a weak and wavering faith. Ask God for help. He is the author and perfecter of faith.
 See Vincent Cheung, Systematic Theology.
 See Vincent Cheung, Ultimate Questions, Presuppositional Confrontations, Apologetics in Conversation, and Captive to Reason.