Only God knows how sincere your commitment was as a teenager, and whether or not you truly gave your life to Christ. Jesus warned us about the dangers of apparently welcoming the Word of God into our lives, then allowing "the worries of this life, the deceitfulness of wealth and the desires for other things come in and choke the word, making it unfruitful" (Mark 4:19).
But in reality, this isn't the issue, because the question you need to face is this: What does God want me to do with my life right now? The answer is plain: He wants you to turn from your sins and your old ways of living, and commit your life without reserve to Jesus Christ. He doesn't just want you to clean up your life (although that's important); He wants you to put your faith and trust in Jesus Christ, and completely turn your life over to Him.
What keeps you from doing this? Only you can answer that question, but I hope you'll face it honestly. Is it a particular sin? Is it a wrong relationship you know you'll have to give up? Or is it simply a desire to run your own life?
Whatever the reason, don't gamble with your eternal destiny, and don't let another day go by without Christ. The Bible's warning is clear: "How shall we escape if we ignore such a great salvation?" (Hebrews 2:3).