<human>: Provide a brief overview of the text.

Please ignore the username... 
So this is a little complicated... My ex (21/f) and I broke things off after 5 years because we were basically just frustrated with all the stress that our relationship brought.  I still loved her, I just couldn't handle the seriousness at such a young age, I guess.  Well, about a week after we agreed to separate, I find out that she did everything but sex with my so called "Best friend."  I was totally in the dark until he confessed through sobbing tears that, in fact, it happened.  This happened about a month ago.  I have cut contact with both of them as much as possible. The "best friend" texted me all the time apologizing and blah blah blah for the past month, but I've tried my best to refrain from reply.  Recently, my ex contacted me telling me how I'm a wonderful person and how she's "completely and utterly broken" and that being with any one else just isn't the same.  She has been with one other guy since this incident, as well.  She continuously tries to explain the reasoning behind her actions and I just don't understand.  I still love her, but I hate her so much.  I am so confused.
<bot>: Ex of five years slept with my best friend... Says she regrets every moment and is trying to stay in contact with me.  So confused.