So my ex and I got back together for 2 months. We have had plans to see IT for months. Now he is taking his 12 year old daughter to see it without saying anything or apologize or just plain dumb asking if that was alright. He didn't ask me to join or we see it later. I'm pissed at him for not being considerate. Him being inconsiderate is usually why I stop talking to him. Should I walk away for good this time?

update: thanks ladies! something small is actually pretty big in this relationship. So keeping my word and moving on!