orthodontist

Hi Doctor,
When I was younger my mom took me to the dentist and he gave me a retainer thing that was like two retainers in one and when I closed my mouth my top and bottom teeth touched it and I had to wear that for a while. Now I am 11 and the dentist sent me to an orthodontist who says we should have gone to him earlier. He told my mom I need braces and an expander and these two herbsts things on the sides of my mouth. When he explained the expander it sounded painful and the herbsts look really big. Do you know why I need this after I had the retainer thing? Are there any other options other than expander and herbsts when you have your top teeth sticking out over the bottom ones and a small mouth?