The most important truth I can tell you is that God wants you to get out of this hole! God loves you and wants you to be filled with faith and confidence and courage -- and He has already given you the means to do this.
What is the key? The key is to focus on Jesus Christ -- who He is, what He has done for us, and what He promises us for the future. How do you do this? The starting point is to make the Bible -- which is God's message to us -- part of your life every day. Faith doesn't grow in a vacuum; it needs nurturing -- and God has provided this for us in His Word, the Bible. The Bible says, "Faith comes from hearing the message, and the message is heard through the word of Christ" (Romans 10:17).
Then ask God to lead you to a church where you can become friends with other believers, who can encourage and help you. You'll also hear God's Word as it is preached and taught, and you'll learn too how to make prayer part of your life every day. We aren't meant to be alone as believers; we need each other.
Just as we grow weak physically if we never eat or drink food, so we'll grow weak spiritually if we never take in the spiritual "food" God has provided for us -- the "food" of His Word, of fellowship, and of prayer. Make these a part of your life every day -- and your doubts will fade.