Here in Africa people go to witch doctors in order to get married, which is a sin. Now can you please tell me if people, who are married by a witch doctor, are allowed to have sex with each other because that for me is a sin. Marriage is from God, and it's considered to pure. Where is the purity in such a marriage? We all know that sex before marriage is a sin, but many people are sinning through marriage that God doesn't allow because of spells, magic and witchcraft. It's also unfair to those being forced into those marriage because they are in contact with sin, thinking that their marriage is from God, but it's actually from a witch doctor. I am sitting in such a situation, and this poor man cries every day because he is married to a women he doesn't love. These are the people you need to help.
The core question is whether a marriage done in a non-Christian environment is considered a marriage.
From God's point of view, a marriage is formed by a covenant (Malachi 2:14). There is no requirement requiring who performs the marriage, nor do you see a requirement that people married prior to becoming Christians must marry again. Instead, we find rules that state that marriages prior to becoming a Christian are recognized as legitimate. "But to the rest I say, not the Lord, that if any brother has a wife who is an unbeliever, and she consents to live with him, he must not divorce her. And a woman who has an unbelieving husband, and he consents to live with her, she must not send her husband away. For the unbelieving husband is sanctified through his wife, and the unbelieving wife is sanctified through her believing husband; for otherwise your children are unclean, but now they are holy" (I Corinthians 7:12-14).
Purity in marriage comes about because those involved save their sexual relationship only for their spouse. "Marriage is honorable among all, and the bed undefiled; but fornicators and adulterers God will judge" (Hebrews 13:4).
Marriages are not forced because the two people entering the covenant do so willingly.
If you don't love your wife, then I must ask why did you enter into a marriage with her? I understand that you don't love her now, but if you willingly entered into marriage with her, then you are violating your obligations as a husband. "Nevertheless let each one of you in particular so love his own wife as himself, and let the wife see that she respects her husband" (Ephesians 5:33). Love isn't a feeling, though it generates feelings. Love is how you treat the person you love. It is not optional whether a Christian husband loves his wife.