How do you tell someone that he is confusing?
or that I am confused by him.
Estoy confudida is what you normally should say. Tú confundes me. That in direct English to Spanish is You Confuse Me. Hope that this helps you a bit.
Me confundes. - you confuse me... or you could say Estoy confundida - I'm confused.
You could say "No entiendo que dice/dices" "I don't now what you're saying" or "Estoy confundido" "I'm confused"