I'm 10 years older than majority of the contestants (I'm just 1 year younger than Hui...) and I'm literally nowhere in life. I take good care of myself but I hate my imperfections that I can't do anything about and I have a hard time embracing them when I see all these perfect idols everyday. So I definitely understand you. Since I'm sort in a rut I'm trying to get out of at the moment, tackling million little problems one by one in hopes I'll see the light at the end of the tunnel one day, I might not have the best advices for you, but I'll attempt to convey something here.
Sometimes it's better to stop looking inside so much and divert your attention outside and to your surroundings. Self-love and self-care are important things, when something happens to you that calls for it, like actually getting some kind of negative feedback from the outside world, on your looks or on your achievements. But when it's not happening, and you're still constantly worried about how others may view you and comparing yourself to others, it borders self-obsession (and unfortunately with K-pop overdoing and in many ways twisting the self-love concept out of its original meaning these past years, it's becoming more and more prevalent for today's Kpop stans). My suggestion to you is to first of all, also try to tackle things one by one because if you look at the big picture of how much of a "nothing" you are, it feels overwhelming. You feel unhealthy? Look up videos on how to live a healthier life. You feel ugly? Look up videos on health and skin care and implement them to your daily routines. Do you have bad habits? Try getting rid of them (I quit smoking 2 years ago, after 11 years! Best decision of my life!) And in the meantime, pay attention to others and see what you can do to make your loved ones' days brighter. Spend more time with your friends and family. Have fun with them, and have deep conversations with them. Help them out with something. Heck, do more chores around the house to lift some weight off of your parents shoulders. The feedback and the fulfillment you get from all of this is what you might just need to actually start loving yourself despite your shortcomings. Also, definitely detach yourself from social media and go outside a lot more. Even just for daily walks around your neighborhood. If you can get your lift your general mood you'll feel more motivated to improve even further.