One of the things you may want to consider is that this is not only a "spiritual" issue. I can relate to this because of my own conversion when I was 20 years old. Up until the time I had converted, I was a touring rock musician - need I say more? In my case, I decided to serve a mission (at 22) and attended (and graduated from BYU). The spiritual change came very naturally to me, but the "cultural" aspect required a lot more time.
First, whether you end up marrying someone who is an active, lifelong member or a convert, you still need to do your best to measure their commitment to the gospel, since this will have a major impact on your happiness in married life (given your background). Secondly, recognize that in spite of our best intentions, habits formed over years are difficult to break. The commandment to remain virtuous before marriage does not only apply to members of the Church. And, as it does with the law of the land, ignorance of the law does not relieve us from the consequences of it, should we choose to disobey.
Repentance, which frees us from the eternal punishment associated with disobedience does little to make the consequences of our immediate sin go away. The way you describe your feelings concerns me. You mention being "hurt" several times in your message and the level of pain you seem to be experiencing leads to me to believe that you may, in fact, be setting yourself up for more hurt in the future if you are unable to resolve this in your own heart. So this really has more to do with you than it does with your boyfriend.
You have, appropriately, decided that there is a certain standard you require for your marriage. If the idea of your boyfriend's sexual experience beforehand hurts you like it does, you may be better off (especially since I assume you are young and still have many years of potential for finding a prospective mate) giving yourself some time, slowing down with the relationship, dating other people and seeing how you feel about it. There is no need for you to rush. Send your boyfriend on a mission - nothing could be better for him. Then reevaluate when he gets back. Take your time and pray about it. Avoid getting into compromising situations with this young man because it will cloud your own thinking and make it difficult for you to receive inspiration.
Above all, don't worry. You'll be fine.