I am really sorry that you feel this way. I do not know what happened 15 years ago but I do know what regrets and guilt over past actions can do. Every so often I find myself cringing at the sudden recall of things done or said in the past. It is hard particularly when those things have involved hurting or disappointing other people.
But let me assure you that no matter how bad the situation may have been, no matter how much pain or anguish you may have caused, no matter how much sin may have been involved, God’s love and Jesus death covers it all. If you have truely turned back from sin to God (and your question certainly seems to indicate this) then you have been forgiven even for what happened 15 years ago and are safe in the love of God.
Paul expresses this so beautifully in Romans 8
An amazing promise and Paul is certain of it because God has done it all for us. If Jesus has died for you and you have put your faith in him then nothing you have done in the past can come between you and God. So rest assured of your salvation!
Now that does not mean that we are free of the consequences of such actions. Sometimes the sins of the past have consequences that affect our future and we have to deal with them - they do not affect our salvation but they do affect our lives. For example an indiscretion earlier in life may lead to driving while under the influence of alcohol and an accident that leaves you disabled - an action resulting in a consequence that affects you even though you have repented of the action many times over. I don’t know what happened 15 years ago but it sounds like it may have been serious and that you may need to make ammends for it (even though your salvation is secure). This may be very difficult for you but it also may be part of the process of helping you deal with the guilt. You may need the support of family and friends to do it. But it also may be a means by which you can show how a Christian manages such things.
How you deal with the incident will depend upon its seriousness and what’s involved. If the incident involved hurting or disappointing someone then you may need to confess that to them, ask for forgiveness and seek to make ammends. How they respond to that is up to them. They may not want to forgive you. You have no control over that. All you can do is confess and ask their forgiveness. If the incident involves breaking the law then it may be more serious - it depends on what you did. You may need to confess this to the police and face the consequences.
So pray about it, asking God for wisdom and strength. Talk with your husband about it and maybe one or two other trusted christian friends. Listen to your conscience and then decide what to do. It may be a really scary prospect but you need to remember that the God who loves you passionately can and will bring good out of all things for those who love him. So do what you think is right and trust that God will do as he promises. I will pray for you as well.
Now about this incident 15 years ago
Let me start by assuring you that nothing that you may have done can come between you and God. I do not know what it is that happened 15 years ago but I