What is happening to me?

What is happening to me?  Right now, I am feeling better but I am still worried that I am not going to Heaven when I die.  I did something I should not have done.  I don't deserve it.  I feel so bad about what I did that I am afraid that it might keep me in Heaven.  I had thoughts about going to Hell. These thoughts are scary in themselves.  I hope to do better.  If I had the faith, then I wouldn't be going through this.