I think everyone has stress these days, even people like you who don't think you should mention it.
Because you are in high school, I might suggest that you try to stop thinking in terms of stress and use that energy to De-stress instead. Proven things to do this: exercise. Have you ever heard of "runners high"? It applies to any sort of physical exertion and if done regularly, will absolutely reduce your stress. And give you a nice, natural, happy feeling.
You must have just started a new school year and that has to be shock to your system after a long hot summer. Try hard Not to pick at your skin, just like when you stopped biting your nails, both bad habits. You can do it! Did you know you can change your behavior in just 6 weeks of concentrated effort to change? It's true. It takes will power, but I think you must have some of that in there.
I hope you have a brilliant school year and I wish you the best as you learn to handle your stress, on your terms.

p.s. "don't worry, be happy." -bobby mcferrin