Do I need to have braces AGAIN?

I'm 13 years old and a couple years ago, I had to get braces. My top teeth have always been perfectly straight, just my bottom teeth are really crowded but my dentist said he rarely only does braces on just the bottom or top because your teeth work as a set. He said that he wouldn't pull any teeth, he said that if I had braces for a year, I'd never have to wear retainers and my teeth would be perfect. So I had braces for a year and my bottom teeth were straight and my tops looked exactly the same as before braces. Then, I got two stupid looking retainers that I could barely talk in that I had to wear 24/7. Then I went on vacation and I forgot them at home. When I got back, my bottom teeth shifted back to their original place. The retainers don't fit right in my mouth. Now, my dentist wants me to get 4 teeth pulled, 2 from the top and bottom, and have a second phase of braces. I had an expander for my top teeth (I don't know why) and my mom had to turn it with a key every day before I got braces, is there a such thing for bottom teeth that would widen my jaw and then my retainer would fit better in my mouth? Or can I just have 2 teeth pulled from the bottom and just get bottom braces? I asked my orthodontast but he looked at me like I was crazy. What do you think? Please let me know. =)