Apparently hearing can be affected by cisplatin... You might have a bit of congestion or swelling behind the ear drum, wait a week or so if it doesn't clear up go back! I woudnt be happy at all. But I think if you were going to have hearing loss due to cisplatin it would have happened during treatment so this may just be an infection of some type - though I am not certain... I'm sure someone here may have an answer for you.
Good luck! Congrats on being seven weeks out! I'm 15!