I totally relate to you, kid. I'm 15 years old too, and have struggled with this anxiety for a long time. I used to be petrified about every little thing wrong with me. I had a slight fever a few months ago, and I literally did not put the thermometer down from my ear for weeks. Whenever my temp went above 98.6F, I freaked out, and because of that, I got warmer, sending my temp up to 99F, and I was convinced that I had a serious illness. All of this unnecessary worrying lead to an upset stomach, and diarrhea, which was my biggest fear besides vomiting... which I had a SEVERE phobia of when I was only 6 or 7 years old. But my anxiety got SO much worse than yours... I'm dealing with issues that you can't even begin to imagine. Please try and calm down. The fact is, things could always get worse, so be happy that you are like what you are now, and I'd do anything to go back to my old self when I was *just* freaking out about getting sick. I went through a period of deep thinking and philosophical thoughts, leading to solipsism and a bunch of other things, including depersonalization, and I didn't even feel *real* anymore. It was a struggle to even get out of bed and all throughout the day I had mini panic attacks and I was constantly freaking out over the face that I was *alive*. I have been coaxing myself out of this dark hole for a week or so now (knock on wood) and I'm feeling better. Now I don't think that I'll ever be anxious about the incredibly useless nuisance to my life of worrying about being sick... because I was scared of life itself. That put things into a major perspective for me. This sounds incredibly harsh and ass-holeish: but to be honest, what you are dealing with now is easily beatable, and its just downright silly.
When you hear the words "thats what help is for" and "there is professional help" and "medication only takes the edge off", I'm sure you worry and think that this is going to be a long, drawn-out process. But honestly, WE'RE FIFTEEN YEARS OLD. Before my dark period of life, I was worrying about getting sick and all that... but it got worse for me because I'm a really deep thinker. But just remember that ***** IS A PERMANENT SOLUTION TO A TEMPORARY PROBLEM. There are people living in dirt shacks in Ethiopia who are struggling to drink sewage to live another day on this earth... and here we are living in a 21st century world with plenty to eat and drink, contemplating ***** because we feel anxious. Take a deep breath and calm down. Watch a movie or something like I did when I felt anxious. Go out and socialize.
**** Also, the root of your problem is *probably* being afraid of being sick, or messing up, or something like that. Take comfort in the fact that those are just thoughts, and they cant hurt you unless you give into them... becoming a self-fulfilling prophesy, making you feel sick, which is what you are freaked out about happening in the first place.