I agree with Nanette's response; her questions and potential answers are completely right. I do not think there is any definitive way to know for sure if you have chosen the right school; it really is subjective and all about how you feel. With that being said, identifying what aspect of your college experience (i.e. social, campus culture, academics, emotional, etc.) is making you question your decision will help you search for potential alternative schools (i.e.. one that is bigger/smaller, has less greek life, has a different set of majors, etc.)
During my first year of undergrad, I asked the same question, as I was not sure if I fit into my school's social scene. For me, as I went into my second year, I started really enjoying my classes, interacted more with professors, met more people via clubs, and solidified my plans to study abroad. All those changes made a big difference and made me more confident in my choice.
Something else that is worth adding is that while choosing a school which suits you is a great goal, college is really what you make of it. If you are open to new experiences (i.e. joining a new club, trying a challenging/interesting class outside your major, studying abroad, doing research, volunteering, becoming a tour guide, etc.), it should go a long way with helping you feel fulfilled with you your college experience.
Hope this helps!