Braces giving me gaps?

I've had braces for eight months, chains and rubberbands for 3 months. Not to long after I got braces I noticed I was getting a gap in between my two front teeth. Before braces, I had no gap an my teeth were overlapping. The chains on top seem to be doing nothing, should I be worried? Also, how much longer do you think I'll need braces for? I'm 16 btw, if that matters....