Question for adults or married people...?

Did you ever say in your teen years "well, I am never going to marry and have children!" And hated the idea of it growing up but now have a spouse and family? I feel the exact same way, and I'm 17 and engaged (don't tell me I'm stupid for doing this) and really have no idea as to why I am. I mean marriage and kids are not something I've ever wanted, and I don't see this as a phase that ill grow out of...everyone always tells me "well I said the same thing when I was young but then got old and married and had kids blahblahblah"...but honestly, I'm just too selfish to start a family or really commit to something as sacred as marriage. Its just something I've never supported, and I've always seen myself as a lone wolf type, living in a flat in a big city somewhere just ruffing it on my own. But I'm trying to see things as my fiance(e?) Does since he is hellbent on creating a family sometime in the late future. Do you think this is just a phase I will grow out of, and come to appreciate the values of marriage and child bearing later on? I've been thinking about this a lot lately and am not sure if I'm getting myself into something ill regret later on down the road...