with Elijah2 (again).
It would not hurt to be baptized again since this time it will mean something more then the first time. but it could be a sign of rededication of life to Lord. I would discuss that with your pastor.
But it is not necessary for salvation or even to do again.
Backsliding is not a term used in New Testament, but was used in Old Testament concerning Israel when they stopped worshipping the one true God and reverted to idolatrous ways.
Lots of people would define a Christian's backsliding in different ways. Here is one way.
What Do We Mean By "Backsliding"?
"The Lord became angry with Solomon because his heart had turned from the Lord God of Israel" - 1 Kings 11:9
"I have this against you; you have left your first love." - Revelation 2:4
Backsliding is when a person who follows Christ turns away from Him. To the backslider, God is no longer the main focus of his life. Without God's leading, the person suffers a lapse morally and reverts back to sin. He "backslides" into his old way of life.
I think it's possible for a Christian to backslide to the point where other believers would doubt the salvation of the "backslider", but I also believe that if the person was truely a believer that God would eventually intervene to help bring the backslider back to following or take the backslider home per, Hebrews 12:
5 And ye have forgotten the exhortation which speaketh unto you as unto children, My son, despise not thou the chastening of the Lord, nor faint when thou art rebuked of him:
6
For whom the Lord loveth he chasteneth, and scourgeth every son whom he receiveth.
7 If ye endure chastening, God dealeth with you as with sons; for what son is he whom the father chasteneth not?
8
But if ye be without chastisement, whereof all are partakers, then are ye bastards, and not sons.
To me, backsliding is not denying Christ, but more an ignoring Christ. It's a dangerous situation, but God is merciful and may allow years of walking away from the Lord before intervening.
I also think, that when a "professed" believer(not truely saved) totally abandons the Christian faith and God does not eventually chasten that person, then it is reasonable for believers to suspect that person was never truely saved, even if there was a profession and even if there was a baptism.
I for one, experienced Hebrews 12, to my shame today. But it came after years of walking away from the Lord, yet I never denied my faith only ignored.
DECISION DETERMINES DESTINY