What should I do about intense sexual desire, knowing that I am capable of marriage but am waiting for the girl I love, and is there a transgression in my delaying marriage?

Marriage is one of the good matters that should not be delayed, due to the worldly and otherworldly benefits it entails. Its greatest advantages include repelling the evils of lust and being a cause for two lives: a fleeting one through procreation, and an enduring one through striving for the hereafter.

It is recommended, and it becomes obligatory for anyone who fears falling into fornication. The crux of the matter is the fear of fornication; whenever one fears fornication, marriage becomes obligatory, even if one is unable to afford the expenses.

If you are secure from falling into fornication, then it is not obligatory for you. However, you must resist thoughts of sex, repent from masturbation, and strive to hasten marriage as much as possible. If you are capable but do not act, then a transgression has occurred.

Your belief that you cannot marry anyone but this girl is merely an illusion, and love can be treated. If there is no way for you to marry her now, then leave her and seek someone else, and ask Allah for help.