<human>: So for starters, I am engaged. I (21, male) have been with her (soon to be 21, female) for 3 years and have been engaged for about 6 months with plans to get married in a few years. We started dating in our senior year of high school after being friends for a good few years prior. We are now juniors in college in different towns, though only a few hours apart. We get to see each other on the weekends, we are still extremely happy together, we have a good sex life, basically a great relationship. We also agreed upon complete exclusivity from day one.

The issue I'm having is that she was my first and vice versa. It has never been a problem before, but recently I have been wondering if as the years go by, I will start to regret only having been with one woman in my life. Cheating is out of the question because both she and I are opposed to it, plus if I did, our relationship would be over no questions asked. Going on a "break" wouldn't be an option either, unless it was a permanent break. I really do want to spend my life with her, I just don't know how I can bring this up to her. On one hand, I could see her being understanding and sharing my feelings to an extent, but on the other hand I can see her blowing up and leaving me.

Can you summarize the given text in a few sentences?
<bot>: I have only had sex with one woman (the one I'm marrying in a few years) and I am worried that I will regret it later on.