All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
First of all, we thank you very much for your trust in us and for writing to us for advice; may Allah reward you.
We ask Allah to increase you in guidance, piety and chastity.
We advise you to supplicate Allah as much as possible regarding all that you wish, as Allah is Most Generous and He answers supplications.
The fact that you live with a religious family is a blessing for which you should be very grateful to Allah. The best way of being grateful to Allah for this blessing, is to perform acts of obedience and avoid acts of disobedience. You should utilize your youth in the obedience of Allah so that you will be among those whom Allah will shade on the Day there will be no shade except His, as confirmed in the Prophetic Sunnah.
We hope that your family will be the best helper for you on the matter of chastity and marriage.
You should seriously think about marriage, as you have become a man and reached the age of puberty, and you are Islamically required to carry out religious obligations.
Therefore, do not pay attention to the thought that you cannot take up responsibility. A person in your situation who fears temptation is obliged to marry if he is capable of meeting the marriage expenses, as stated by the jurists.
For more benefit, please refer to Fataawa 84026, 87295, 90384 and 84254.
If you are a student, then do not make studying an obstacle. If the your financial ability is the reason (of not getting married), then you may find a pious woman and her family who will accept you as you are, and will be satisfied with your limited means. Besides, marriage is one of the means leading to richness as Allah promised this in His Book. Allah Says (what means): {And marry the unmarried among you and the righteous among your male slaves and female slaves. If they should be poor, Allah will enrich them from His bounty, and Allah is all-Encompassing and Knowing.} [Quran 24:32]
Furthermore, Abu Hurayrah narrated that the Prophet said: "There are three kinds of people whom Allah will certainly help them: the Mujaahid (fighter) in the Way of Allah; the Mukaatab (the slave who has a written deed of emancipation in return for a sum to be paid in installments to his master) who wants freedom; and the one who wants to marry therewith he seeks chastity." [At-Tirmithi and An-Nasaa’i]
If you don’t succeed in getting married, then do all things that would help you keep your chastity and avoid what incites your desires. One of the most important means to keep yourself chaste is to fast and to do all other acts of worship in general. Other helpful means are attending circles of knowledge and faith, keeping company with righteous people, and utilizing your free time in what benefits you.
We do not know why you mentioned that fasting is useless for you. In any case, there are other means.
As for Zina (adultery or fornication), then you must beware of it. Allah, The Lord of the Worlds, warned us against it and described it with the most heinous descriptions. Allah Says (what means): {And do not approach unlawful sexual intercourse. Indeed, it is ever an immorality and is evil as a way.} [Quran 17:32]
You never know, if you commit Zina, then Allah may become angry at you because of it forever, and you may have an evil end when you die.
It was said that Zina is a pleasure of one moment (short period) that causes regret for a year (a long period).
If we presume that you become overwhelmed by desire, and you are about to commit Zina, then in this case you may masturbate. Even though masturbation is forbidden, but it is a lesser evil than Zina.
The footnote of Al-‘Adawi on Sharh Al-Khirashi, in the Maaliki School of jurisprudence, reads:
"Know that masturbation is forbidden, whether or not one fears to commit Zina. However, if he cannot repel Zina except by masturbating, then he should opt for masturbation instead of Zina as a way of committing the lesser of two evils.” [End of quote]
Allah knows best.