Many readers probably feel the same way you do, and I often get letters like yours. But God doesn't want our faith to be shaky and weak, and He wants to help us become strong in our faith. The Apostle Paul's prayer applies to us: "I pray that out of his glorious riches he may strengthen you" (Ephesians 3:16).
How can our faith become strong? Let me point out three ways. First, be sure of your commitment to Christ. Is your faith in Jesus Christ and what He did for you by dying on the cross for your sins? Sometimes a person's faith is weak because he or she has never clearly taken this step of commitment. By a simple prayer of faith ask Christ to come into your life today–and He will.
Second, build your faith on the truth of God's Word, the Bible. The Bible is spiritual "food" given by God to strengthen us in our faith. Through it we learn of God's love for us–but apart from it our faith will always be vague and uncertain. The Bible says, "Faith comes from hearing the message, and the message is heard through the word of Christ" (Romans 10:17).
Finally, draw strength from other believers. If you're not active in a church, ask God to lead you to one where Christ is preached and you will have opportunities to grow spiritually–not just in the weekly service, but through Bible studies and other programs.