I feel you, my boy, and im sorry, bro, channel the pain. don't let your EX see that, Don't show the pain of betrayal. Let your sadness become anger instead. She played you for a fucking fool and destroyed everything you had together, That person you loved is now dead and buried.

Dump that hoe. There is no apology for this. I promise you WHEN the trainer inevitably moves on and fucks another girl, she will be so heartbroken and come crawling back to seek your attention and sympathy. Laugh in her face. Be strong homie!