Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.

For fornication, it is one of the great and major sins which Allah abhors. Not only does the Qur’an prohibit adultery but also just approaching this sin. In the Qur’an, we read the following verse: “And do not approach unlawful sexual intercourse. Indeed, it is ever an immorality and is evil as a way.” (Al-Israa’17:32)

Prophet Muhammad (peace be upon him) included adultery in the most cardinal sins. Ibn Mas`ud reported: “I asked the Messenger of Allah ‘Which sin is the most serious?’ He replied, ‘To attribute a partner to Allah, though He Alone has created you.’ I asked: ‘What next?’ He said, ‘To kill your child, fearing that he will share your food with you.’ I asked again, ‘What next?’ He said, ‘To commit adultery with your neighbor’s wife.’” (Al-Bukhari and Muslim)

Prophet Muhammad (peace be upon him) confirmed that a true believer cannot commit adultery and one cannot have faith in Allah while committing adultery. He said: “When an adulterer commits illegal sexual intercourse, then he is not a believer at the time he is doing it; and when somebody drinks an alcoholic drink, then he is not believer at the time of drinking, and when a thief steals, he is not a believer at the time when he is stealing; and when a robber robs and the people look at him, then he is not a believer at the time of doing it.” (Al-Bukhari)

You should repent this sin and all other sins. On how should you seek forgiveness from Allah, you have to make a since repentance.

First, your repentance should be meant for the pleasure of Allah. It should not be intended for showing off.

Second,  you must express remorse for the sin you have committed.

Third, you must give up this sin.

Fourth, you must have a strong resolute not to make this sin again.

Moreover, you must increase of your righteous and good deeds. You must also close all cracks and avenues that may give room for the Shaytan such as mingling with men or talking to them without a legal reason.

It is permissible to have a miscarriage as long as the infant did not reach the age of 40 days. After reaching the day 40, life has most probably been given in him. This is the view of a large number of scholars who belong to the four schools of Islamic law.

Getting married is not compulsory. If you both like to get married sooner or later you can do that. It is preferable you get married because it seems that being unmarried was one of the reasons you did this sin.

Almighty Allah knows best.