I have/had the same problem.
I'm 21 but, my mom also isn't tolerating most of my decisions.
My solution to all kinds of getting support in my decision is to do what I have to do and let happen what has to happen :). Usually people don't treat you as a serious person until you do not have some background that proves your decisions to be correct. With parents it's harder because they are used to you being a child.
So short version of my strategy: think well, and do what you feel is right. Don't quarrel with people that may help you (like parents), just try to make them understand that this is really important to you. And after a time they will see that you're doing well, maybe better than themselves, and will treat you as an adult.
This is life, it's not easy ;)
P.S. Maybe getting married can help, but I won't be able to tell you in near half of the year, and your problem shouldn't be a reason for marriage 100%.
Have a nice day