I've never had a cavity before and now I have 11.

My dentist said cavities are normal in the teen/early adult years (I'm 19) but this feels like allot to me. I need a root canal on my bad tooth and the rest are just regular fillings and maybe 2 crowns. Is this going to hurt? Is it really normal for teenagers to have this many cavities because it feels like allot. It's mostly my molars that need the work but some canines too.