Maybe it happened slowly. You stopped feeling anything when you prayed. Or maybe it was one terrible event, and afterward nothing made sense. Now you are not sure what you believe, and you feel guilty, or sad, or just empty.
You are not the first. A father in the Gospels felt the same mix, and said it out loud to Jesus.
The father and his son
A man had a son who had been terribly sick since he was a small child. The boy had fits that threw him to the ground and into fire and water. The father had tried everything. He brought the boy to Jesus's followers, and they could not help.
When Jesus arrived, the father begged him, "If thou canst do any thing, have compassion on us, and help us."
Jesus repeated the man's words back to him: "If thou canst." All things are possible, Jesus said, to someone who believes.
Help my unbelief
The Gospel of Mark, one of the four accounts of Jesus's life, records what the father cried out next.
And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief.
Mark 9:24 · King James VersionThe original Greek
εὐθὺς κράξας ὁ πατὴρ τοῦ παιδίου ἔλεγεν· Πιστεύω· βοήθει μου τῇ ἀπιστίᾳ.
Found in Codex Vaticanus (about AD 325), Codex Sinaiticus (about AD 350).
The oldest copies are shorter: "I believe; help my unbelief." The words "with tears" and "Lord" appear in later copies.
In the oldest copies it is even shorter: "I believe. Help my unbelief." Five words in the Greek.
He was honest. He believed, and he did not believe, at the same time. He did not pretend. He asked Jesus to help with the part of him that could not believe.
And Jesus helped his son.
What you can do
Be honest with God. You can say, "I do not know if you are there." That is a prayer too. It is what this father did.
Do not rush. Faith that comes back slowly is still faith.
Talk to someone safe. A friend, a pastor who listens, someone who will not panic or lecture you.
Read the stories of Jesus again. Not the arguments. Just what he did. Many people find their way back through the person, not the rules.
Let go of what was never his. Sometimes what we lose is a version of God that was harsh or frightening. That may need to go. Jesus is still there when it does.
You are not a lost cause
The father did not have perfect faith. He had a sick son, a little belief and a lot of doubt. That was enough for Jesus. Whatever you have left is enough to start with.