You should have disclosed it early. Any way, you have to go for gradual disclosure, so that they should not take it as shocking news. Your mother already smelled about it few years back, you open this topic with her. Try to tell her still you like him and you are serious about him. If she gives positive response then go ahead and tell her you want to marry him. If she rejects, tell her that you are having relationship with him since last 7 years and still he has not ran away. This is a proof that he is serious too. You may require to disclose your sexual relations with him and try to convince her if he is like his friend, he would have flown away. Your relationship has survived for 7 years that itself is one positive point. Issues regarding state and native place are secondary and that can be settled if they accept your relationship in a first place.