I've been engaged for two months, but lately I've been feeling like I'm too young to be tied down?

My fiance and I recently had a long, tearful discussion that revolved around me feeling discontent and like I'm going to lose my independence once we get married, even though the time we set for the wedding is over a year from now. He told me that he feels like if I can't confidently say that I would want to be married tomorrow (hypothetically, not actually), that he doesn't want to be kept on the back burner until I feel more ready. We ultimately decided to try to make it work, with the condition that if it worked out in the next few months, we would elope before I went on my summer abroad. Unfortunately, although I agreed at the time, I can't stop thinking about how soon that would be. I don't know how to broach the subject at all, and I'm afraid that by broaching it the relationship would end, because it's getting to the point where I feel some time apart may be best. Any advice?