It sounds like you are very conflicted about your sexuality. You are scared to have intercourse and yet have been willing to masturbate. Now that you've heard that masturbation is a sin, it sounds like this form of sexuality is on the verge of being ruined for you also!
It sounds like your religious beliefs that are standing in your way. As long as you thought masturbation was acceptable, you were unconflicted about masturbating. Now that you've heard that this is a sin, you are terrified to masturbate.
So, it sounds to me like religion is the culprit. First of all, when religious texts speak about masturbation, they are talking about male masturbation. I
n the olden times, it was believed that tiny little humans lived inside sperm; so if a person masturbated, it was considered tantamount to killing another human being. Obviously this isn't the case. So, maybe you can chill out a little bit on the masturbation being a sin business.
As for having intercourse with your boyfriend, if your religious beliefs tell you that premarital intercourse is a sin, then you are going to have a very hard time being comfortable in having intercourse with him.
If you can feel comfortable again with mutual masturbation, at least you will be able to give and receive pleasure in non-intercourse ways. This should tide you over until you are married.