Confused and Out of Place

My friends would always say, “You don’t look like your sister, and sorta, but not really like your brother. You don’t really look like anyone in your family as a matter of fact.” I would feel lost, out of place and confused, not knowing how to explain it. When my mom told me I was egg donor conceived, it all made more sense, but I still feel out of place.
I’m almost 16 years old and my mom just told me a couple weeks ago that I am conceived from an egg donor. I freaked out because for the last 16 years of my life, I believed her to be my genetic mom and always wondered why I didn’t really look like her or my sister. My sister looks like my mom, my brother looks like my dad and I always believed my face got deformed or messed up somehow.
My sister is from my mom and dad’s eggs, so I’m genetically her half sister. She’s known for a couple years now. My brother is from the same egg donor I am, but he does not know he is conceived from an egg donor. I have no idea how he would react if he was told because he’s been known to have a temper and I think my mom is afraid to tell him.
I have no one to talk to about this issue. I believe my sister would have the mindset of “get over it, you’re still my sister,” my brother doesn’t know and my dad would check back in with my mom before he told me anything. I asked my mom a few times if we could enter information into the sibling donor registry or if I could see my biological mother’s profile and she always replied, “not now,” or “Don’t be ridiculous” or “I’ll find the profile later.” When she first told me, my first reply was, “I love you mom,” and I kept my feelings to myself but freaked out via texts to my best friends.
I love my mom and I believe her to be the best mom in the world, but I still want to know who my genetic mother is. She’s scared I’ll replace her, but I would never do such a thing and I wish she would see that and be open to me finding my biological mother. It would be comforting to find someone who looks like me, and would help me understand where I fit in.
To parents who think of withholding information from their child – don’t. It only makes things more complicated later on in life. They’ll find out at one point, whether it be by you telling them or finding out after you’ve passed away. The feeling we feel when we find out are that of betrayal, confusion, and a strong need to find our biological mother. By holding this information from us, you just create tension and will break your family apart. Too many secrets – keeping a family together is stressful enough, you don’t need any secrets screwing with the balance of things.