I ask Allah to forgive all our sins and to guide us all to the straight path. First of all, we should agree that premarital sex is absolutely prohibited in Islam and it is one of the grave sins which may end up with other major sins if a person does not hasten to quit and return to Allah for forgiveness and repentance.

One should also be aware that many times he loves something which may be a cause for his misery. You are in need to uplift your belief and regain your relation with Allah by stopping this relation right away and resolving that you will never be back to fornication. You must show that out of sincerity and love for Allah.

My suggestion is that as long as he is a Muslim, you must work on improving his iman and increasing his confidence in Islam and you get married to him after explaining the situation to your mother and convincing her that this is the least harm possible instead of being more indulged in an unlawful relation. I ask Allah to shower all His mercy upon you and to make things easy for you and for him.

Almighty Allah knows best.