Challenged By The Ex And She Won!

So my boyfriend and I went to a wedding last weekend where we have a mutual friend with his ex-girlfriend. I explicitly told him not to talk to her the whole reception and here's why.

She created a fake facebook account of a guy and told my boyfriend it was her so they could drop hints to each other on each other's wall about hookin up or whatever. Write messages back and forth. All it would look to me is like he's too into some dude and flirting on turning the corner to being gay. Needless to say they went too far and I figured it out.

That was about 6 months ago. Now we knew she was gonna be at this wedding so I told him don't even look at her. So I go to the bathroom after the bridal dance and come back to find them in a corner almost face touching. I freaked out and no lie grabbed the microphone off the DJ and called him the biggest cheating profanity I ever knew and left. A pin could drop after that and everyone looked at him.

Here's the thing. He's mad at me over it! It would have never happened if he would have been understanding about how I felt about him going near her. He already broke trust once. It makes me even madder that he is mad over anything.