Hey, it's not like it's the end of the world. You're so young in a few months you'll be up looking for the another leading lady. Date around, see what you like, see what you don't and have a little fun. And to add there are plenty of little ladies who wouldn't even dream of cheating on a man.
Oh and just remember you're not to blame for her cheating but you didn't do a lot of things you needed to be doing. Remember that. There are a lot of ladies who need to feel wanted, desiered, pretty and loved. You must show this regularly, pay attention when a lady is crying out for attention. If you can remember that the next time around you're golden.