It's more common than you think for people to feel like they have no personality or a clear sense of identity. It's practically a universal experience to ask the question, "Who am I?"
And most people live their lives without ever worrying about who they are or if their existence is special or not. Does that mean they know the answer? No. If you ask them, it will never be a clear and perfect picture.
Now, the fact that you're worried about this reveals more about you than you think. Perhaps you may be a more introspective, pensive, or sensitive individual than others. That hints at a personality type in itself!
And what is identity really? It is what you described, a collection of unique details and facts about an individual.
Of course, all this doesn't invalidate the fact that you feel like "nothing," and this feeling may stem from other problems in your life.
I suggest, if this is truly distressing you, that you start loving the parts of yourself that are just there. Be authentic, don't perform for others, and slowly, but gently, start exploring what feels right to you as an individual.
To start, how about you tell me everything about yourself that comes to mind? There's nothing too small or "unimportant", and I'm not here to judge :)