It's always good to both know how engaged is the other part, in case any would like to go slower (or faster I guess). And it's important to be honest at it, cuz maybe saying "I love you" sounds like you are probably exagerating right now. Sure, you feel a strong conection, but how much do you actually know the other person to tell then that?

So, tell them you are falling hard for them, but wait some (months? Weeks? Idk mate you just feel it lol