How soon did you realize that you loved your significant other?

My boyfriend and I knew each other when we were freshman in high school. He moved out of stare when we were juniors. Now we are 23 and he is back in my life. We've only been officially dating for a week, but I know that I love him (not in love,yet). I kinda feel stupid admitting it. But just the way he treats me and how his paternal instincts kick in when he is around my 5 year old and 9 month old nieces makes me want to spend the rest of my life with this man. 

Is it too soon to tell?