Boyfriend got a message that I’m cheating

Honestly, I would never have thought this could happen to me, at least not at this age anymore. My boyfriend of 2 years received an Instagram message from an anonymous/makeshift Instagram account claiming that I’ve been cheating on him with a long time friend from school. The worst, is he has trauma from his last relationship where his girlfriend of 3 years cheated on him.

I’m in shambles and disbelief. He almost didn’t believe me, until I let him spend 10-15 minutes going through my phone, it was the only thing he said would confirm if I cheated on him. Our relationship is so strong but I never thought someone could do something so nasty and wicked. I haven’t even seen this person they claim I’ve slept with for almost a year.

I’m traumatized, not knowing who, If someone even close to me, would plot something so horrible that would almost end our relationship. My boyfriend trusts me after he found nothing in my phone, but I’m having the hardest time sweeping this under the rug. I’m so stressed and exhausted. I do no harm to anyone, who is after to make my life miserable?! What are they going to do next? I’m sorry for the long message... I just never thought this could happen to me. 😞🥺 I cant stop thinking about who it is and why they would do this.