What you did was wrong in God's eyes; God gave our bodies to us, and He wants us to take care of them and use them for His glory. The Bible says, "Therefore honor God with your body" (1 Corinthians 6:20). Perhaps your letter will be a warning to someone else who is abusing their body in some way.
However, only one thing will keep you out of heaven, and that is your refusal to accept God's free offer of salvation in Jesus Christ. Elsewhere in your letter, you admit that you have ignored God most of your life - but I pray you won't do so any longer. God loves you; He loves you so much that He allowed His Son to go to the cross for you. Now He offers you salvation as a free gift - free, because Christ has already paid for it.
What must you do? Think of it this way. Suppose someone offered you an expensive gift. They had paid for it, and now they wanted to give it to you. But what would you have to do? First, you'd have to believe that they really wanted it to become yours. Second, you'd actually have to reach out and accept it.
The same is true with Christ. He paid for your salvation with His own blood, and now He offers it to you as a free gift. Believe it - and then receive it into your life by trusting Christ as your Lord and Savior. Don't delay, because "now is the time of God's favor, now is the day of salvation" (2 Corinthians 6:2).