No, this is not true. If you have truly repented of your sins and are trusting Christ as your Lord and Savior, then you can be confident that God has forgiven you freely and fully.
Do you remember Peter? He had been a loyal follower of Jesus from the beginning of His ministry and yet after Jesus' arrest, he stood around a fire outside the place where Jesus had been taken and denied that he even knew Him. The Bible says, "He (Peter) began to call down curses on himself, and he swore to them, 'I don't know this man you're talking about'" (Mark 14:71).
And yet Jesus still forgave Peter! Not only that, He welcomed Peter back as a disciple, and he went on to become a bold and powerful witness for the Gospel. Just a few weeks later, Peter urged others to experience the same forgiveness he had found: "Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins" (Acts 2:38).
Don't be shackled by doubt, or by a fear that God might not forgive you because of what you did in the past. The devil wants you to believe this but it isn't true! If you have sincerely received Christ into your life, then you are forgiven. God's promise is for you: "God has given us eternal life, and this life is in his Son. He who has the Son has life" (1 John 5:11-12).