How do I delete groups on facebook?

Okay so my high school marching band made a facebook group page and I cant join it because this thing keeps popping up telling me I joined too many groups on facebook. So I tried looking for groups I joined and I didnt join any groups. I dont have any pages on facebook. I guess I did join groups ,but how do I delete groups if I dont see them? Please help...this high school marching band group page is really important because it informs me about things.