OH problem! 😡

Soooo yesterday, I went to lunch with my sister and friend, and my partner rang to see what I was up too.. 5 minutes later he walks into the same restaurant with a girl who he knows I strongly dislike and completely ignores me and sits down with her to have lunch and then leaves with her! 😡 I am so so angry with him, I ended up staying at my Mothers house last night because I didn't want to be around him.. But yet he is struggling to understand that it was wrong and disrespectful?! What do I do?! I feel like punching him! 👊