First time realizing mom didn’t love us equally

I fell down a flight of stairs with my baby sister in my arms when I was eight and instead of catching myself I used my body to shield my sister. My sister was totally unharmed, just got scared and started crying ofc. My mom rushed to the stairs and ripped my sister out of my arms, she started hitting and yelling at me. I didn’t hear what she said because I had stopped breathing and wasn’t able to focus atm. I got the wind knocked out of me, my back was so injured I couldn’t walk for days afterwards (I’m still in pain 12 years later actually, might have to go to the doctor soon to get this checked lol), I had a concussion (I hit my head HARD. It was one of those stair that has a long part and then a little part that goes a different direction, I unfortunately fell down the long part and hit the wall head first), I was covered in bruises head to toe the day after. Also got some nailmarks (now scars) on my arm from my mom grabbing me and throwing me off the stairs (I wouldn’t stand up when she was “talking” to me, little did she know I was currently not breathing or able to stand so I just fell to the floor). When I was finally able to breathe again I cried for hours because I was in so much pain. My mom told me I was being dramatic and that protecting my sister was my duty as big sister so I should just be happy that she wasn’t injured. Oh how I love being the oldest child.