Love and Marriage....take 2

So, I have recently gotten engaged to a great man that I love and my family adores.
This will be my second marriage, but the first one that is done right (I eloped the first time). My mom is excitedly planning the reception and the church has already been reserved. I have my bridesmaids and have picked out my colors. I should be excited, right?

I AM PETRIFIED!!!!!!!

My first marriage was not a good one. I married him to get away from home and while I knew him for 5 years before we got married, I realized shortly after that I did not know him at all.
My ex was military, and not just any service, He is a Marine. Now, I knew him all through highschool as this mild mannered, shy, really sweet guy. That is the guy that I fell in love with. After bootcamp, he completely changed (as most of them do). He acquired the god complex and thought his self so much better than anyone else, including me. We were married for 4 years and he cheated on me a total of 5 times. Because he is a Marine, women around the base flock to them for financial security and to get out of their little towns. He apparently didn't say no. Especially when he went away on Debt. The women in other countries loved him. My question always was, Why marry me if you wanted to be able to go out with other women? Then answer I figured out after my divorce, and that was that he didn't want to be alone. The military sent him out to the other side of the country and he wanted someone there that he knew as comfort. As soon as he was comfortable, I was no longer required. He ended up leaving me for one of the girls that he cheated on me with.

So my worry is this, (quite obvious) What if this happens again? My fiance is not military (not going there again), however, he was a virgin when I met him. Not only in the sex sence but also in the relationship sence. What if he realizes down the line that he wants to have more experience and doesn't want to settle with the first girl that he was with? What will I do then? The thought is really scary. I want to say that I know him, and that would never happen, but that is what I thought with the first one too. How do I get over this? I don't want to ruin something that could be great with my worries, but I can't get hurt like that again.