The One and my only first love

I know this has been has been debated many times, but who truly believes there is your “one” with love at first sight. I’ve been with this utterly amazing man not for long, yet I feel like he is my person. He never uses the word if, only when. Plans are ours and not just his and we have talked about kids and marriage. Being together for such a short time concerns my family and now making me slightly nervous. Day one of us meeting I just knew I need him in my life. Should I be concerned that this is just infatuation? Or might this be my life long story.