Thanks for your question. I am sorry that you’re feeling so anxious about this - but the good news is you don’t need to be.
As you seem to already understand, the great news of Jesus is that we have been forgiven of our sins and reconciled to God because Jesus died in our place. The Apostle Peter puts it this way"For Christ died for sins once for all, the righteous for the unrighteous, to bring you to God.” [1 Peter 3:18]. Similarly, Jesus famously said “For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.” [John 3:16]
So the great comfort and assurance Christians have is that the forgiveness of sins and the promise of eternal life has already been paid for by Jesus death on the cross on our behalf. There is NOTHING we can do to earn our way to be friends with God. Christians call this ‘grace’. That is, God has been generous to us by graciously forgiving us, even though we do nothing to deserve it.
So it doesn’t matter how much we do, God has done it ALL for us in Jesus. It’s interesting that at one point the disciples ask Jesus “What must we DO to do the works God requires?” Jesus response was “The work of God is this: to believe in the one he has sent.” [John 6:28-29]. The only thing we can do is to accept God’s offer of forgiveness of sin and the gift of eternal life by putting our trust in Jesus.
So if you believe that Jesus is your Lord and Saviour then you can be 100% guaranteed you have done enough to be a Christian. Of course, following Jesus as Lord means submitting our whole life to him, turning away from ungodly living etc. To help us do that we are encouraged to meet with other Christians so we can be learn more about God, be encouraged in our walk with him etc.
With regard to baptism, I am afraid the person you heard say baptism ‘was the only way to get into heaven’ is mistaken. Water baptism is a good thing for Christians to do - as it is a visual sign of what happens when we are ‘baptised with the Holy Spirit’ [Mark 1:7-8; John 3:5]. However, it is not a condition of eternal life and there are instances in the New Testament where believers weren’t baptised [Luke 23:39-43].
So let me encourage you to rejoice in the assurance of your salvation as you continue to follow our Lord & Saviour - Jesus.