Thomas was one of Jesus' closest disciples; he had heard Jesus teach and seen Him perform many great miracles. And yet after Jesus' crucifixion, Thomas' faith was shattered, and when others enthusiastically told him that Jesus had been raised from the dead, he refused to believe it. Only when he met the risen Christ face-to-face did he exclaim, "My Lord and my God!" (John 20:28).
But I want you to notice two things about this incident. First, notice what Thomas did: He stayed with the other disciples. He didn't turn his back on them, nor did he decide to give up his search for the truth. Instead he wanted to get his doubts resolved, so he went where he thought he could find Jesus -- and he did. Jesus' promise is for you: "Ask and it will be given to you; seek and you will find" (Matthew 7:7).
In addition, notice that Jesus promised to accept anyone who came to Him by faith in the future. He said, "Blessed are those who have not seen and yet have believed" (John 20:29). God loves you just as much as He loved Thomas, and He wants to remove your doubts and come into your life.
Begin by reading through one of the Gospels (I suggest John) to discover who Jesus is and what He has done for you. Don't let your doubts enslave you, but ask God to show you His truth -- and He will. Then act on it by giving your life to Jesus Christ.