Oh gosh. My friend. :C you are amazing. You are beautiful. You are a worthwhile person. Your weight, your body shape, neither of those means that you are not worthy of respect and love. You are worthy of respect and love at any size. Everything your mom is telling you is complete garbage meant to make you feel bad. This is the same shit I heard from my parents, and it damaged me for years and years. Trust me when I say the scale has nothing to do with your worth.
I want to share with you something that made a big difference in how I saw myself, and how much self worth I had. Its a blog called Shapely Prose, by Kate Harding. I would start here https://kateharding.net/2007/11/27/the-fantasy-of-being-thin/ and then go all the way back to the beginning of her archive, and read forward, it helped me a lot.
But please, whatever you do, don’t believe your mom. You are worthy of respect, and love no matter what you weigh or what you look like. You do not deserve abuse for your appearance.