I been married for about twenty years. Several years ago I had an affair with a man that went on for a few years. I gave myself to this man: mind, soul, and body. My husband found out, but I lied about the sex. He is asking me again. Should I tell him I had sex with this man? I know God forgave me, but I heard you don't have to say everything that happened. Is this true? Am I going to hell if I don't tell him everything?
You are sinning because you lied on top of committing adultery. I'm glad you repented of the adultery, but lying is just as wrong. "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).
If a spouse doesn't know about an affair that has ended, has been repented of and likely will have no future impact on the marriage (like a child from the affair), I typically suggest not saying anything because it won't do the marriage any good.
But in your case your husband did find out. In this case you do need to tell him the truth because he asked. Do you need to tell him exactly how many times you were in bed with this bum, or what sexual positions you used? No. If asked, you can politely state that the affair is over and you don't want to revisit it. You can even mention that you don't want the man you love to be jealous about a man who encouraged you to sin and whom you discarded.
Thank you for your answer. But I forgot to tell you. My husband will hit me if I tell him truth if he asks. So I'm afraid so I have to lie.
The problem is that your statement is a lie. Lying is never required. To say you have to sin to avoid someone else sinning is also false. "And why not say, "Let us do evil that good may come"? --as we are slanderously reported and as some affirm that we say. Their condemnation is just" (Romans 3:8).
Your husband striking you is a possibility, but not a fact. If it does happen, then you deal with that sin in an appropriate manner.