It would not be weird, but if you've only been dating for one week, and want to retain your friendship, you might think about this. See how the actual "dating" part goes. If it isn't working as well as you might have expected then having told her you love her might mess up the actual friendship.
In other words: If the dating part does't work out, do you still want to remain friends? How do you think she feels? Test the waters out and see if she indicates her feelings are as strong as yours are in this matter.
Each individual is different, but I would see how the dating part actually goes - but I would certainly not wait another four years. A few months might be long enough - but also don't wait your life away. How old are you, by the way? Are you young, in high school, or are you much older?
And, why has it actually taken you so long to begin dating?