I'm a Christian and I am a praise and worship leader and a Sunday school teacher in my church. For a while I have been struggling with my fiance to not have sex, even though we started before but not completing it. However, today we did have sex, and I don't know how to repent because I feel like I've reach God's limit. I have asked Him to forgive me, but I still wonder if He accepts it. I honestly want to serve God the right way, but how do I repent of something I enjoyed? Should I still lead praise and worship?
There is nothing in the New Testament about praise and worship leaders. Even if one could decide that such a position exists, you run into the problem that women are not allowed to lead in worship. "Let your women keep silent in the churches, for they are not permitted to speak; but they are to be submissive, as the law also says. And if they want to learn something, let them ask their own husbands at home; for it is shameful for women to speak in church. Or did the word of God come originally from you? Or was it you only that it reached? If anyone thinks himself to be a prophet or spiritual, let him acknowledge that the things which I write to you are the commandments of the Lord" (I Corinthians 14:34-37). You have taken on a leadership role in violation to God's command. "But I do not allow a woman to teach or exercise authority over a man, but to remain quiet" (I Timothy 2:12). If you want to serve God in the right way, then you need to start with living your live as God teaches. "But why do you call Me 'Lord, Lord,' and do not do the things which I say?" (Luke 6:46).
It appears that you put your personal feelings ahead of God's commands. You know fornication is wrong, but because you enjoyed it you conclude that it wasn't really wrong for you. You asked God for forgiveness, but you have made no commitment to turn from this sin. I can only conclude that you aren't totally convinced that you did something wrong or that you aren't fully convinced that you are accountable for your actions. "But I will show you whom you should fear: Fear Him who, after He has killed, has power to cast into hell; yes, I say to you, fear Him!" (Luke 12:5).
If such is true, it would explain why you kept flirting with fornication. You kept telling yourself that as long as you didn't have actual intercourse, then it wasn't so bad. But in doing so, you completely missed Jesus' point: "But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart" (Matthew 5:28). Lusting for sex when you aren't married is just as much as sin as the actual act. You and your fiance have been involved in lewd behavior, which is also sinful. "Let us walk properly, as in the day, not in revelry and drunkenness, not in lewdness and lust, not in strife and envy. But put on the Lord Jesus Christ, and make no provision for the flesh, to fulfill its lusts" (Romans 13:13-14). Likely you two have been engaged in sexual talk. "But fornication and all uncleanness or covetousness, let it not even be named among you, as is fitting for saints; neither filthiness, nor foolish talking, nor coarse jesting, which are not fitting, but rather giving of thanks. For this you know, that no fornicator, unclean person, nor covetous man, who is an idolater, has any inheritance in the kingdom of Christ and God" (Ephesians 5:3-5). Yet all of these sins only bothered you a little, if at all. You went on pretending that you were a faithful Christian, up until you think you might have crossed some imaginary line, and even then you aren't certain.
You need to see God for who He truly is. "Therefore consider the goodness and severity of God: on those who fell, severity; but toward you, goodness, if you continue in His goodness. Otherwise you also will be cut off" (Romans 11:22). You need to leave the world of churches that teach man's doctrines and find a true church that follows God fully. "Enter by the narrow gate; for wide is the gate and broad is the way that leads to destruction, and there are many who go in by it. Because narrow is the gate and difficult is the way which leads to life, and there are few who find it ... Not everyone who says to Me, 'Lord, Lord,' shall enter the kingdom of heaven, but he who does the will of My Father in heaven. Many will say to Me in that day, 'Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name?' And then I will declare to them, 'I never knew you; depart from Me, you who practice lawlessness!'" (Matthew 7:13-14, 21-23).
Honestly, for a while I just couldn't grieve. I felt like my heart was cold. But now I can feel my heart breaking. I just don't know how to get back to that place with God. You are right but know I just don't know what to do.
Emotions are not repentance. They may spur you to repent but it is what you actually do that brings about a change. "For godly sorrow produces repentance leading to salvation, not to be regretted; but the sorrow of the world produces death. For observe this very thing, that you sorrowed in a godly manner: What diligence it produced in you, what clearing of yourselves, what indignation, what fear, what vehement desire, what zeal, what vindication! In all things you proved yourselves to be clear in this matter" (II Corinthians 7:10-11). You have to make up your mind that you are going to live life God's way, regardless of the way you feel.
This isn't just about your sexual sin. You have been going your own way without knowledge of God. As God told Israel: "My people are destroyed for lack of knowledge. Because you have rejected knowledge, I also will reject you from being priest for Me; Because you have forgotten the law of your God, I also will forget your children. The more they increased, The more they sinned against Me; I will change their glory into shame. They eat up the sin of My people; They set their heart on their iniquity. And it shall be: like people, like priest. So I will punish them for their ways, And reward them for their deeds" (Hosea 4:6-9). You are not with a church that teaches the truth. That is a huge hole in your life.
As an example, few denominations teach the whole truth about salvation from sin. Look at What Saves a Person? and What Must I Do to be Saved? Ask yourself if you have fully followed God in this matter, and if not correct it.