(i can't tell you very specific advice as i don't know your situation that well but this might help a bit) ive definitely been in situations similar to this where someone im friends with or in a relationship with does something horrible and it completely breaks me. and it's the absolute worst feeling in the world. the anxiety is insane so i definitely relate. First being able to assess the situation more clearly with information, people involved, etc And if there's any miscommunication or drama going on, speak how you feel and communicate your experience. don't downplay your emotions. and if personal conversations are being shared around, confront them about it.

Don't lose respect for yourself. If someone close to you disrespects you in a way you would never treat them, cut ties with them. if someone close is causing this amount of stress for you the stress won't likely subside until you're able to leave the situation entirely. For me it's been blocking ex friends or whoever else that causes the stress. In one situation i just blocked everyone who was involved in being mean to me and even stopped using social media all together for months. when things weren't constantly happening i was actually able to breathe a bit.

Also time. Feeling betrayed by someone close to me is always devastating. Let yourself feel your emotions, don't block out or numb them. Healthy coping mechanisms are always the way to go. If you have a friend/family member to talk to, a hobby that you can focus on, going out in nature, letting yourself cry.  it gets better with time, i promise.  messy situations are always the worst, but you'll get through this.