My darling, here is the problem. Like jcr279 said, its very hard to understand the right techniques when you havent had lessons. The thing is, if you don't start singing properly now instead of belting from your throat (which is one of the worst things you can possibly do), you have the chance of developing numerous things with your throat. You CAN wreck your voice ocmpletely if you keep singing the way you are, and being in musical theatre, its not a good thing.
Being Adelaide isn't such a bad thing. Because she has a very charctery sounding singing and speaking voice, you can work with that. If you can't sing (which im sure you can), just work with your director on some voices you can use with Adelaide. REMEMBER: musical theatre isn't just about sounding pretty, its about having influction in your voice and bringing a character to life.
Good luck doll!
You've gotta have heart AND music