this isnt really very fair on your girlfriend is it???
finish it with your girlfriend because a relationship is about wanting to be with that person not about thinking about somebody else everytime you kiss your crrent girlfriend etc.
and how do you know you'll end up in an another relationshp?
if you serioslii want this other girl that you've known since you were 4 then you wunt end up in another relationship
wait for her
she'll soon come round if she see's you're waiting for her