Britt--
Being sixteen is very hard--both for gals and guys. I'm not going to tell you that your romance with Josh was "only practice"--your emotions were deeply involved and Josh's duplicity was very painful.
Guys, much more than girls, are tempted to play the field; to see just how many conquests they can accumulate. This is very hard on girls/women.
Fortunately you're starting a new school year. There is enough routine built into your days, Monday through Friday, that you can't sit around and coddle a broken heart--or convince yourself that a cracked heart is broken.
Obviously you're going to be interested in whatever Josh is doing in the foreseeable future, but you're being very mature about not phoning him and whining and weeping.
If Josh is a 'love 'em and leave 'em" guy, the more independent you are, the more attractive you are to him.
I wish you luck, Britt. Learning the rules of living and loving can be very painful--but we all have to learn.
P.S.
Check out these poems by Dorothy Parker. She's very soothing for a broken heart.
http://www.americanpoems.com/poets/parker/sort_poems_alphabetically#poems