Menewsha Avatar Community - Ex-Boyfriend is Dating Ex-Best Friend? How to Deal?

Let's start from the beginning, shall we?

About three months before the end of the last school year, I was perfectly happy. I had a group of best friends, a loving boyfriend, and a supportive family. Then everything changed within a day. My friends had been acting normally all day, but suddenly pulled me aside at lunch and started throwing insults at me, reducing me to tears. They told me that I'd changed, that I always lied, that I had a different best friend every day. None of it was true, yet I still wracked my brains for a reason as to why I could be different. My family was in the process of moving, and my grandma had just been sent to intensive care. When I told them that, a certain friend, Katherine, said, "that's not an excuse." I didn't understand; I wasn't acting any differently than I had before... Why were they doing this?

The next day, I caught them talking to my boyfriend about something. I didn't know what, because they wouldn't let me anywhere near them. It turns out that Katherine had been telling him to break up with me because I would cheat on him with his best friend if given the opportunity. That was totally ludicrous. He and I were both torn up, crying in class, and generally unhappy. I couldn't understand why he would believe her, or why she was telling him this.

At this point, no one was talking to me except for my boyfriend, because of Katherine saying such horrible things about me. She actually cornered me at school and started insulting me, my boyfriend right by my side. He didn't do anything. It was truly miserable at school. We all went on a class trip to Disneyland and acted cordially, and then school was over.

Summer was rough. Every day, I noticed that my boyfriend was talking more and more about his best friend, Katherine. How he was over at her house, (no one ever goes to her house...), and how he started calling her "Kat". (no one else does...) At that point, I decided to tell him how I felt about her, and that him talking about her so often was kind of uncalled for. He apologized, and after another confession from me, assured me that he didn't have any romantic feelings for her. Yeah, right.

We hung out on the Fourth of July and watched the fireworks and had a great time together, everything seemed fine. Actually, I was hoping that he'd break up with me then. (I couldn't bring myself to break up with him, although I needed to. I really was head over heels in love with him.) Of course, he didn't. He waited, dumping me three days before my birthday through a text. That really bothered me, although it was my fault for not breaking up with him.

Next thing I know, he's dating Katherine. It didn't surprise me, but that didn't make it hurt any less. I was utterly crushed, and confused. He was perfectly happy with me until she started insulting me and treating me like trash. I didn't understand why he would leave me for someone who could be so cold. Frankly, I still AM crushed and confused. I see them together all the time, and it tears me apart.

The worst part is, none of my friends are on my side. They all think that Katherine's actions, (and my ex-boyfriend's) were totally legitimate. I understand that people have their own will, and that they can date who they want. It's just... Why those two? The girl who ruined the last months of school for me? My ex-boyfriend? It doesn't make sense, and I don't know how to deal with it, because I'm totally alone. My current best friend even told me, "I can't give you any sympathy, I'm really happy for them."

How do I fix this broken heart?