I am a born again believer, and i am going to marry a person committed to the Lord. We are engaged and we are waiting for the marriage. During these times we indulge in a little phone sex. It ends up with me ejaculating. Is it ok or is it a sin? We are not touching each other. It's only through phone that we talk about what we would like to do after marriage.
I cannot compare this to pornography which is lusting after other women and it is a sin. But how about your girl whom you have already engaged.
Please give your valuable feedback. If it is a sin, I am ready to cut it off and obey God wholeheartedly.
As Jesus taught, sexual sin isn't restricted to the physical act of sex. "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). Lust is just as much a sin as actual adultery. "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).
The flaw in your reasoning is that while you are not lusting after many women, you are still lusting after a woman to whom you are not married. Yes, you have a commitment and a plan to be married one day, but it hasn't taken place. And there is no guarantee that it will take place -- none of us know the future. Just as it is wrong for you two to have sex while engaged, it is equally wrong for you two to be inflaming each other's passions before marriage.
There are several problems that you create for yourselves. First, because this is based on your imagination, you are setting yourselves up for unreasonable expectations. Reality will never match imagination. Second, you are priming yourselves for giving in to temptation. There are going to be times when you are alone and the temptation for sex before marriage will be harder to resist because your conversations have been sexual. Third, it is easy to slip into the topic of sex dominating conversations, but sex is only a minor part of a marriage relationship. You should be spending time getting to know each other better as people -- not objects of sexual desire.