I want to learn gymnastics without taking cles or spending money,but on my own.how do it?

I'm 15 and I've always wanted to learn gymnastics. Like I don't want to compete or anything its just something I want to learn. Like flipping and stuff looks so fun and free to me and I just want to learn. But to take cles of course costs money and I'm kind of embarred because I'm a so underweight and skinny in leotards due to being anerexic and I can't do anything. Not even a cartwheel so I don't really want to do it with a bunch of people watching. So is it possible to teach yourself some stuff? Like how dangerous could it get and could I learn everything or does some stuff require a teacher? And how long do you estimate it would take me to get really good since I won't have a teacher?