AIO? my boyfriend cheated on me with my bestfriend at my bday dinner

So I (18F) just had the most humiliating experience of my life. My boyfriend (19M) and I have been together for almost two years, and my best friend (18F) has been like a sister to me. Last night was my 18th birthday dinner, organized by my parents with all my friends and my boyfriend there to celebrate.

Everything started great, but I noticed my boyfriend and my bestfriend acting suspiciously close. Like they are good friends and I was happy about that. At first I ignored it but their behavior became too intimate. Later, my friend told me she saw them kissing earlier in the night some people got up to use the restroom. I confronted them in front of everyone, and my boyfriend denied it while my bestfriend admitted to it. She tried to excuse it as a mistake, and my boyfriend looked guilty af.

I went crazy, ended things with my boyfriend on the spot and was shouting at them in front of everyone. Now, the fallout has been huge. Some friends support me, while others think I overreacted and should have handled it privately. Mia has been messaging me claiming it was a mistake and my ex wants another chance, but I’m done.

I feel heartbroken and humiliated, having lost both my boyfriend and my best friend. Was I wrong to confront them publicly and did I overreact?