You are not alone! Almost every (if not every) Christian battles with doubt about really being saved.
Romans 10:9 -
“Because if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved."
Salvation cannot be earned. If that were the case, none of use would stand a chance. All have sinned, and regardless of what those sins are, without God’s grace we deserve death. But thankfully, anyone can accept Christ and Psalm 103:12 mentions that as far as the east is from the west, so far has He removed our transgressions…
That means all sin has been wiped clean past, present, and future.
However, the Bible makes it clear that repentance is the key. This means submitting your life to Him. It doesn’t mean we’re perfect, but it’s a change of heart and direction.
The good news is, God is understanding. We all mess up. If you read the Bible, some of the most godly men did terrible things, and yet God forgave them (like David who committed adultery and then had someone killed). The point is that you always come BACK to Christ. You truly repent and continue living for Him as best you can.
Again, we are NOT saved by works and you cannot lose your salvation. People can willingly walk away from Christ, but that is a person’s choice, not because they suddenly lost their salvation.
Rest assured that if you truly have accepted Jesus into your heart (claiming Him to be your savior) and then from this day forward you trust Him with your life and continue to live by faith, you are saved and nothing can pluck you from His hand.
As for the mental health, I highly advise both seeking professional help if not done already but also finding a church in your area. Reach out to a pastor and get involved in a small group and explain you’re new to the faith. This is how you grow as a follower of Christ