No, you do not need to be baptized again if your baptism was undertaken in response to the true Gospel. The Bible teaches that God's offer of eternal life is conditional. It is conditional on our repentance and the way in which we live. If we do not attempt to follow the example of Jesus, even though we might feel we have been 'saved' we will not inherit the kingdom of God. One of the New Testament writers uses the example of Israel in the wilderness to show that God does destroy people who have been saved if they do not continue in their faith.
Jude 1:5 I will therefore put you in remembrance, though ye once knew this, how that the Lord, having saved the people out of the land of Egypt, afterward destroyed them that believed not.
That's why there is forgiveness. People who are not baptized into the saving name of the Lord Jesus Christ do not have access to forgiveness of their sins. If you have been baptized in response to the true Gospel then you do have access to the forgiveness of your sins when you backslide. Such forgiveness is still conditional upon real repentance and a sincere desire to reform one's life. We must remember that God wants people to be saved, but on His terms.
2 Peter 3:9 The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us–ward, not willing that any should perish, but that all should come to repentance.
So we see that there is an obligation, once we have 'put on Christ' to continue serving Him. If we serve him sincerely then there is forgiveness when we sin or backslide as you put it. There is no need, in those circumstances, to be rebaptized.
Here is a link with information about baptism which you will find useful:
Why Baptism REALLY Matters: https://www.thisisyourbible.com/library/show/178
I hope you have found this helpful.