I'm so sorry that happened to you and I really know how it feels! When I was 18 I was "with" a guy and found out he basically had two other girl friends. Even worse we worked together. So I quit my job but I was still heartbroken for months afterwards. We had a lot of fun together and everything. But I guess since I didnt physically see him cheat my mind could only remember the good times. It really helped me to write down all of the hurtful and shady things he did in a list vs the list of good things which started to look shorter and shorter.

Also, when I started dating my now bf I basically forgot about the guy all together! You will find someone who's really worth your time one day:)