I think I committed a lust. I thought of having sex with a person I knew, and really do regret it, after I found out it is a very big sin. No one told me it was a sin, but after I've done some research, I found out it is as if I am actually going it, meaning having sex before marriage. After realizing what I've done, I really began to regret it, and I am not ever going to do it, I promised myself. Does this mean I am going to hell, and I will be punished? Or is God going to give me a second chance? I really need to know of it, as I was never aware of this happening to me. I never knew about it either.
All sin, unrepented of, leads to a person ending up in hell. God doesn't rate one sin as being bigger or smaller than another other than by the number of people affected by a sin. Whether a person ends up in hell because of being a coward or because of murder, the result is the same. "But the cowardly, unbelieving, abominable, murderers, sexually immoral, sorcerers, idolaters, and all liars shall have their part in the lake which burns with fire and brimstone, which is the second death" (Revelation 21:8).
The solution to sin is also the same, no matter what sin you have committed. See: What Must I Do to Be Saved?