I'm going to walk away from my gf at disney world in front of our friends because she was yelling at me for making a phone call to my ex about my son
Oh no, why did you need to call your ex about your son? Did your girlfriend not want you to call your ex?
She started yelling at me and I got furious so I hit her and walked away.
I can understand why you are upset but you also wrong for hitting her. You shouldn't yell at your partner and she needs to understand that you will be communicating with your ex because you have a son together. You should also try and control your anger and not hit people because you will wind up in jail.
It's her fault for being angry. At least I was able to handle myself.
I don't think you were able to handle yourself if you hit her. She was wrong to yell at you and be angry, but you were wrong to hit her, as that is a physical assault. I do hope you apologize to her and promise that you won't do it again, as hitting her often is an abuse and you may regret doing that with someone that you love.