How much would it hurt to have few extracurriculars/little leadership?

I’m a sophomore and I go to a highly rigorous school. I’m already working extremely hard to maintain good grades, and next year my courses I’m planning to take will likely be much more difficult than they are now. I don’t think it would be a good idea to drop any of them because I made a few unwise decisions in courses this year.
Also, I got stuck in really difficult math courses my first two years and they took up a lot of time on weekends (literally entire days studying for tests.) Thankfully, that’ll be over soon.

I’m also not really much of a leadership-type person. I’m a soft-spoken person and I can’t really see myself running a club or anything of that sort. I’m a member of two clubs and in any case, in both of them I feel unqualified to hold a board position. I also do band and that takes a lot of time out of my day to do other things. I play tennis and I think I could make varsity, but that’s pretty much it.
I’m also into computer science but I only started recently and a lot of people at my school have been coding since before high school, and a lot of people are very advanced.
I feel like I’m not doing enough extracurriculars and I see other people doing so many things outside of school. I feel like I won’t be able to handle a lot more on my plate, but somehow other people are doing it.
I’m applying for a couple of things for next year but if I don’t get them, I’ll have very few extracurricular activities.
At this rate I probably won’t have a lot of things to write about come college admissions, and I’m worried that this could really hurt me, even if I have good grades and good test scores. I understand that I shouldn’t be doing activities outside of school just for the purpose of college but I can’t help but think about how having so few could impact my admissions.
Any advice?

You seem to have some extracurricular activities as you play an instrument as well as do a sport. You’re also apart of some clubs. When you have an opening in your schedule or find an opportunity, you can search for some places to volunteer at as volunteering is pretty useful in my opinion. I’m sorry that I don’t know much about how it impacts your admission to colleges, but they are slightly important because they show colleges that you have time to juggle your grades along with clubs and sports, etc. Also with computer science, you seem pretty well-rounded, just take a little bit more maybe.

You should choose your activities according to what will work best for you and what you feel is meaningful for you. High school is not all about developing a resume for college. It is mostly about being engaged in activities and classes that are most likely to allow you to become the type of adult you want to be. Along the way, you have to do certain things, like take tests, for college application. But don’t let your entire high school be about college. Take what works for you. I have posted this link many times. It is relevant to all students regardless of the type of school they may apply to. It is: http://mitadmissions.org/blogs/entry/applying_sideways

^ Good point and I agree, I mean, it’s not useful if you don’t actually enjoy what you’re doing.