What would be the solution to this problem?

I have had braces for 4 years and last month I asked my orthodontist how much more time is needed (he told me around 5 months). 10 months ago my orthodontist gave me elastics to fix my overbite. After wearing the class II elastics for this amount of time, my top teeth starting shifting back and my bottom forward. Unfortunately, this caused my bottom teeth to move too far forward. I do not mean that my jaw is too far forward, I mean my teeth are. It almost looks like an overjet on my bottom teeth. My orthodontist is currently trying to move those teeth back so my bite can be corrected. In a normal bite, the bottom teeth stand up straight, but in my bottom teeth lay forward (but my jaw is in the correct place). Last month he told me to put on class III elastics to bring my bite back. It helped a little. Currently, he put a chain on my bottom front teeth. I believe they moved back a little but they still need to go back. I am a little worried that it might take longer. I wanted to add that I always wore my elastics 24/7 because I really want the process to go by faster. So my question is this: Why did this happen to the bottom of my teeth and how long would it take to fix it? Also, what can I do to help my bottom teeth move back to where they used to be (straight up)? I know that brushing helps but what else?