Help I feel dumb but I want to be smart, where do I start?

I may be coming down hard on myself but I feel dumb for some reason. People always tell me I'm smart but I just want to know more, more and more or else I feel dumb; especially when into interaction with people who are more knowledgeable in certain subjects than me. I'm still a teenager, but I want to know more about politics, psychology, economics, business, philosophy, space, ecology, science, math(not so much though because I seriously just don't get it sometimes, ever), ect. ect. ect. I just have a thirst for knowledge but I feel like I'm not learning anything! I just graduated high school and have just had this sudden urge to learn everything I can but I don't know where to start, what to read, what to start teaching myself. I'm about to start college in 2 months but what do I learn in the meantime? Do I just go to the library and just pick any one book from each category I want to learn about?