Omg OP I feel your pain !!!
My parents decided to call me one name. For some weird reason they decided to give me a different First Name, and then a Middle name that isn't even what I'm referred to either !?!?
My name is a nickname for my middle name, but it's not a common nickname , so people get very confused when I say my full name. They always ask me "if that's your full name, where does xxxx come from?
" , as they haven't heard the nickname connection before.
I'm reading all these comments like "if this is the biggest problem in your life , you have an easy life" and "you're making this into a big deal , when it isn't". Trust me, it IS a huge problem.
I NEVER know what name I'm registered under, anywhere.
My degrees don't match my cv name.
Different ID's have different names , so nothing matches.
Not understanding someone is calling out to me, when they call out one or either of my "other" names.
Having a different name at school / college register.
Oh just EVERYTHING ! It honestly affects me very regularly !
Even on my wedding day, I had to sign some form declaring that NameA + B and name C is the same person :/
Imagine not being referred to as YOU, on your own WEDDING DAY ! It feels so alien.
I think I could have coped better if it was just my middle name, as I think people understand this is more common. But being a nickname of my middle name has really affected me throughout my life 
I will not be putting my own kids through this.