Hit me for no reason

So my mom has been talking about how my brother been stealing from my little brother and I said something and she said "that's stupid" and I thought she said I'm stupid so I said "I'm stupid" and she said no "yeah your stupid and what Gonna do huh" she started pushing on my head and my arm. I'm sensitive so I'm gonna cry "she asked why was I pouting for and she hit me in my arm.. That's when the tears started coming down.. She started Calling me fake and a cry baby and I'm trying to figure out like why did she hit me Cuz I thought she called me stupid