What is a real IQ test actually like?

I'm known as a very smart person, but sometimes I worry. I mean, I'm super lazy, and don't work hard at all, so my grades have always been average. Like everybody, I am paralyzed by self doubt, so, if it were to be that my IQ was average, I would have nothing at all to be proud of. I mean that, I'm not handsome, fit or, social. That and my sister outshines me in every way humanly possible, I'm serious, imagine something and she is better at it. My one thing that is impressive about me is that I'm presumed to be Intelligent however, that may not be true...so I've never actually taken a real IQ test. I did when I was younger, and I did super good, especially in the reason section, but that was more than 10 years ago. Are they similar to online IQ tests? I'm 24 if that matters? and I constantly contemplate suicide...not that I would admit that...I don't have friends...because I'm quiet, and self-hating...I only got a 24 on the SAT...anyway-IQ tests.