It would probably sound the most natural to say: "I am a little disoriented today because I took such a long vacation." Hope this helps! :)

Hi, Nao Something can be disorientatING But people are/feel disorientatED Also note: so+adjective (so long) such+adjective+noun (such a long vacation)

I am disoriented (or disorientated) today, because I had such a long vacation.