There are a lot of folks that don't know what they want to do in life. I'm one of them, just to put that out there. I don't know anything off the top of my head that I could really enjoy and find fulfilling. I'm currently working a dead-end job that's absolutely mind-numbing. I can definitely tell you where I don't want to be. If you have the opportunity, try a few jobs in different fields. Maybe you'll find some inspiration.
As for who you want to be, that's completely on you. Your moral compass will help guide you, if you listen to it. The best thing about being a human is that nothing is set in stone. If you wake up one day and decide "I don't like being a doormat", you can formulate a plan and execute it. You can completely change how you interact with the world.
Lastly, I really do think that, unless you have some kind of mental illness, that your personality really is you. There may be aspects of it that you do or don't enjoy, and that's fine. There are certainly ways of influencing and changing your personality. That'll happen over the course of your life. Experiencing more of the world and the people living on it will, most likely, have an effect on you and your personality.
I think that if you were ever to completely quantify your entire personality, you'd probably be a robot. Self-discovery is an exciting and unsure adventure!