Boyfriend left me for my best friend

Nerhys
Okay so in 2015 me & this guy started dating & we dated for 2 days short off a year. We never actually broke up he just Unfriended me on Facebook he wouldn't talk to me & my friends would ask us if we were still dating & we both would say idk until about a month later someone asked him & he finally said no we're not (THANKS FOR F**KING TELLING ME AS***LE) before we stopped talking I was in & out of hospital for month so I barely got to see him at school, I think during this time I was in the hospital he was flirting with my best friend. He then openly let out his feeling about my best friend & I told her I'd hate them to date it would hurt me so much, & she said she didn't like him anyway so there was no issue, about a week later they started dating & she didn't tell me, another friend did. They've been dating for about 2-4 months & it still hurts me so much & it's so awkward to be around them but I tried to ignore my best friend & talk to all my other friends but they talked to her instead of me so I'm forced to talk to her because my other friends wouldn't support my decision to not be her friend anymore. 
I'm so hurt 😔 it literally makes me feel sick to my stomach having to be around them. 
(I'm in the purple shirt, my "best friend" is leaning on my shoulder & that's my ex boyfriend/ her boyfriend 🤧😔 next to her) 
I just don't know what to do.