Islam does not encourage or approve of suppressing anyone’s legitimate and natural desires. Rather, it helps to realize those desires in a decent and legal way. If one’s wife loses interest in sex, the husband should urge her to seek medical advice and even psychological counselling. If there is no way out, then Islam permits a man in such a situation to marry a second wife, to satisfy his natural needs and at the same time to maintain his wife. Islam does not allow the man to resort to any illicit relationship to relieve his sexual urge.
The prominent Al-Azhar scholar Sheikh `Abdul-Majeed Subh, states the following: Seeking sexual gratification outside marriage is not lawful. Rather, it is prohibited as Allah Almighty says: (Those who guard their sexual organs except with their spouses or those whom their right hands possess, for (with regard to them) they are without blame. But those who crave something beyond that are transgressors.) (Al-Mu’minun 23: 5-7)
Thus, as a Muslim husband and couples generally, you should strive hard to satisfy your sexual urge within the wedlock. You are not allowed to resort to any other form of gratifying your sexual urge save through your wife. You can arouse her sexual desire by hugging her and using appropriate foreplay. You can even threaten her with marrying another woman if she refuses to share your bed, but you are not allowed to gratify your sexual desire outside the wedlock, as I have stated. You should also inform her that refusing to have sexual intercourse with you is a sin and she should refrain from doing so. The Prophet (peace and blessings be upon him) is reported to have said, “If a husband calls his wife to his bed (i.e. to have sexual relation) and she refuses and causes him to sleep in anger, the angels will curse her till morning.” (Reported by Al-Bukhari)
If all ways to gratify yourself within the wedlock prove fruitless, then you are allowed to marry a second wife to fulfill your desires within a lawful marriage, but you are not allowed under any circumstances to seek gratification outside marriage in any form.