How to convince older teenage son to take better care of himself?

My older son is 19. He's had allergies all his life that cause sneezing, congestion, sinus issues, etc. but now that he's basically on his own, he has been extremely lax about taking his allergy meds. On top of that, in spite of the fact that we are right on the beach and have a pool, he's decided that he'd much rather spend all of his free time at his buddies places, inside, playing video games. So he's pale as a ghost and has all the symptoms of a vitamin D deficiency. He also has a habit of taking various items and "cleaning" his ears (car keys, cotton swabs, etc.) but he does it extensively like he'll sit there and watch an entire movie digging away absentmindedly in his ear.So in most cases, let the kid figure it out on their own, maybe give them some advice here and there, right? Well in our case, he also has medical anxiety. So he is constantly coming to my wife and I in a panic, because he has been having severe sinus headaches, or his ear feels weird and it's throwing off his balance, or he's exhausted all the time and never feels like doing anything, etc. He has insurance with zero copay and a brand new car. Yet he won't go to the doctor for any of this. He won't even take his allergy meds that we still buy for him. He won't come outside and get some fresh air and exercise. He won't stop finding whatever he can and digging in his ears for hours.If he wasn't constantly coming to us all freaked out about his symptoms, I would just figure he needed to figure all of this out on his own but I'm honestly fed up with it. I've told him to go see the doctor if he's got health concerns, I've explained over and over that not taking allergy meds has always given him horrible sinus headaches, and that he was warned by his doctor years ago that habitually cleaning his ears was a bad and could mess with his inner ear.I have also been trying to get him into therapy for what is obviously a case of hypochondria or anxiety for years and he refuses to go. I know I can't force him. I'm just over it. I want him to feel healthy and I understand that he's feeling like crap lately but if he won't do even the simplest things to help himself, why should we have to listen to him go on and on about his worries and concerns all the time? Do something about it, kid! via /r/Parenting http://bit.ly/2Xs3P3i