My mom isn't my real mom...

I'm not trying to sound ungrateful, I'm really not, but I'm so sad and hurt rn😞. I'm 15 and I've always been a mama's girl for as long as I could remember and we have always had such a strong bond. My mama(if I'm even allowed to still call her that) and my dad sat me down today to show me my birth certificate... It had another women's name on it. They said they wish they told me sooner, but they thought it was best at the time... My biological mother was a women who didn't want me to begin with. She was on drugs and didn't take care of me. She was my dad's first wife. My dad was being abused by her and after I was born it only got worse and she pushed me down the stairs when I was learning to walk. My dad finally left and got full custody. From what I've learned about her she was abusive and got her son from another father taken away for abusing him. She died 11 years ago from an overdose.

How am I supposed to take that?! I just found out my mom isn't my mom. Shes just someone who decided to put up with me. I'm not fully related to my siblings. I'm just their half sister. And it just makes me question so much. There's no way my mom could love me as much as her biological child.... I'm a step child... That's what I've always been and thats what I always will be... My biological mom didn't even want me. Also this means I have a half brother out there. Its all so much... I feel like everything has changed..😢😢😢😢

* So I talked to my Mama and I apologized for getting so upset. She said it was okay and hugged me and let me cry a bit. I understand she is still my mom and I love her so much. I really wish she my biological mom though😔. I'm also very curious about this half brother I have out there but I don't think now is the time to think about it.