Alto? Mezzo? Soprano? So confused!?

So, I'm pretty sure I'm not a soprano. I can sing as a soprano, but then I sound very raspy and weird. I think I'm an alto because all of Rosie's songs from Bye Bye Birdie are perfect for me. But lots of people say my voice sounds like a mezzo. I have the ability to sing as a mezzo, but my voice feels more comfortable as an alto. What is my vocal range? Am I simply an alto-mezzo?