I'm mad at my boyfriend for getting a tattoo without me
Did you want to get a tattoo also?
No, but he didn't consider how I would feel about it.
I'm sure that you felt disappointed when you found out he got the tattoo, but you can't dictate what your boyfriend does. Let him know how it made you feel, but accept the fact that he can make his own decisions.
I have every right to get mad that he didn't tell me about it or ask for my permission. He was wrong for doing it and shouldn't have done it. I think I should break up with him because I can do better.
You really cannot tell a boyfriend what to do or not do. If you act like this long term relationships will become a challenge for you.