commitment?

Okay, I feel like I've committed to this guy at such a young age. I'm 18 and want to experience things in life but wish I could just do it with out feeling like I'd loose him. We have been dating for about 3/4 years now. Highschool sweet hearts and all. However, I realized that there is so much I haven't done and that I will meet other people as I grow. (This isn't just about getting dicked down by other guys btw).I don't know if I just like the security of knowing that I'll have him to fall back on or something like that . I love him with all my heart and every part of me knows that. But just knowing that there is a whole world out there to experience bothers me and makes me feel like maybe I'm missing out. Idk honestly. Have any of you guys felt this way? What do you think about this? This might not even make sense. I'm just ranting.