Hi :) I'm responding to this at your request.
I know what you're going through, and I know what it's like to feel scared too. As I was saying in one of your other topics, I seem to worry about something different every day too. Not to the extent that you do, but some days can definitely be worse than others.
To be honest, I really have no idea about throat cancer or what the symptoms of it are; I'm completely clueless when it comes to diseases like that because to be honest, I'm not a doctor. The only knowledge I have of the body is the introductory biology class that they make us take as a General Education class in college. I would find out more about diseases and the body, but Googling and researching things about that on the Internet only make my anxiety worse. Speaking of that, reading about NPD or throat cancer online and taking those quizzes is really something that you need to stay away from. Those quizzes are very inaccurate. See, a person can be a bit narcissistic sometimes, but that doesn't mean that they have the full disorder. But anyways, about the throat cancer, I think it's really unlikely that you have it. It's more likely that you have extreme anxiety over it. I worry about similar things, but I'm alive and healthy, typing this message. I thought that there was something wrong with my heart, but I had my doctor listen to it and I had an EKG, and she said that it sounded perfectly healthy. For your own peace of mind, you should get checked out by your doctor. It really helped to lessen my anxiety.
I do know a few things about psychology and mental disorders, and I'm pretty sure you don't have NPD. I actually know someone with NPD. My friend's sister has it. And as sixpack up there mentioned, people with NPD wouldn't know that they had such a disorder, and they would flat out deny having it if someone pointed it out to them. They wouldn't care either. I told you this before when you were worried about having schizophrenia and/or being a sociopath: the fact that you're so worried about having the disorder proves that you most likely don't have it, even with the supposed symptoms you pointed out. In fact, you sound like almost the opposite of someone with NPD, in my opinion.
For example, one of the classic symptoms of NPD is the lack of empathy, but you clearly have empathy for other people, with all of the examples that you mentioned, like the guy on Youtube whose dream of being a singer made you cry a little when he actually achieved it, or how you try and surprise your mom by cleaning the kitchen to make her happy. And as I mentioned before, people with NPD simply wouldn't care if they had any of the symptoms that you pointed out. And some of the symptoms you pointed out are just completely different. You said that you're shy, indecisive, and sometimes worried about your appearance and what other people might be thinking about it. These are not symptoms of NPD. I'm honestly curious why you think you have it. About the other things you mentioned, they're honestly not that strange. People arguing with each other always feel like their opinion is the right one. Everyone feels greedy or protective of their money sometimes, and most people will brag if given the chance. I'm around your age, and I still don't know what I want to do with my life either. Extreme laziness can be a symptom of your ADHD. I have ADD, and when I don't take my stimulant medication to correct for it, I'm extremely sluggish and lazy too.
You really really need to slow down, and maybe see a therapist. I know that it's not an easy step, but they can really really help you. You have a psychiatrist, but honestly, just seeing a psychiatrist isn't enough. A therapist can be sympathetic, helpful and friendly. Anyways, I hope I was able to to help you in some way.