My boyfriend (25) went on vacation with his ex (26f) without telling me (21f)

I'm in shock. He hasn't told me anything about it. I found out through the ex's instagram story (boyfriend doesn't know I follow her on a fake account). I am on vacation with my family right now. Didn't even know he is out of the country.

Also, my boyfriend still hasn't told his ex about me even after 2 years of being together. She doesn't know I exist. They were together for 5 years before we started dating.

I feel fucking betrayed and don't know what to do. Am I being cheated on? Is there any way I can stay with him? I don't want to leave but I'm afraid I have to.

TL;DR: I'm an idiot

Edit: rules

Submitted July 14, 2019 at 12:47AM by thehippiewitch https://ift.tt/2NUEChK