I'm going to fire my personal trainer because he wanted me to eat better
Why would you fire your personal trainer for that?
He wanted to have a great looking client.
While you can fire whomever you want since you hired them, the trainer is just trying to help and he has no ill intent. His goal is to help you lose weight by exercising and eating right so it's not smart to stop that.
I just don't want to diet.
I understand it's hard to diet, but it's very important to watch what you're eating when you are trying to lose weight. You should consider listening to his advice.