I have been insecure about my body for 7 years now (since I was 7 in 2014) read description...?

And I watch body positivity tiktoks and the people in the videos are either plus size or have perfect toned bodies, an nothing, absolutely NOTHING has worked not 1% to boost my body confidence and I feel like I'm getting even more insecure. I feel like a slight amount has to do with me comparing myself to others, but I've been doing that since I was 4. That's just how I am and nothing has been able to change that. But comparing myself to others isn't too much of the problem cause when I look at myself I don't think about anyone. I just don't like how I look an have extreme trouble teaching myself that my body is beautiful. (My description: short, underweight and skinny, hasn't been able to gain weight, bloated tummy, has cellulite.) Those were just some of the things I have been insecure about since I was able to be self conscious about my body. I just want to know: why have I been so insucure before I even started puberty?!?!? Why is nothing helping? (Btw I've learned to stop comparing myself to others)