I think that being a graduate student at age 18 could have some downsides. Basically you would be way younger than the other students.
Another thing to think about is that at least in my experience most (not quite all) of the students in my master’s program had some work experience. Personally I had two years of work experience doing software engineering in a math-heavy environment after I got my bachelor’s degree and before I started graduate school. Similarly my other family members (who are in different fields, mostly health care related) had some work experience before applying to graduate programs.
I also wonder if you would want to study as an undergraduate for a year or two just to have the experience. As one example, you might want to get a second bachelor’s degree. Math and computer science are for example two fields that go together quite well. Similarly you might see if you can get involved in research at your local university. If you could do research for a couple of years, you might get some university social experience, plus perhaps even get paid something, and get experience that would be valuable before applying to graduate programs.
Can you discuss your options with a professor at the local university where you are taking courses?