Korean doesn't say it like this " there's no doubt I'm in love with you" you just simply say 사랑해요! sometimes if your really serious you it can be said 진심으로 사랑해요~ ♥ in korean the most common way people use "to be in love" is (나는/난) 사랑에 빠졌어요=which just means "I'm in love", you can tell this to other people, but if your talking want to tell someone you love them the most common/natural way is just 사랑해요