The fear

Tonight, I was talking to my fiance about the future and what things we were planning on doing. There was a moment in which I said that I wanted to see a lot of the world, and he replied with a 'we'll see' comment. This brought on one of many small panic attacks I've had since I've been engaged; but this one had a particular mark on it: what if I'm throwing my life away by getting married at such a young age?
I've always mocked the girls who get married out of college or high school. I never thought I'd be one of them. During the summer, I came to the realization that I was in love and that this man would help me make my dreams come true. Now, however, I find myself asking myself daily, "What is love? What does it feel like?" Sometimes I worry that I haven't felt the right thing, yet; and that I'm just going into this because it's the right thing to do rather than the right thing for my heart.
I'm now sitting here pondering what I want to get done in this life. Can it be done with husband in tow, or am I throwing some of it away for the sake of "love"? Should I be worried about this? Yes. Now? Of course.
But, really, what is love? What is this concept? Is it just a physical reaction--a bodily function--used to keep the population up? Or is there something else to this? Am I missing something in this storm of emotion?