He will not hate you if you say no - unless he's a jerk and in that case you don't want him anyways.
They say you can't change someone, but I am not sure that is true. I've seen women quickly mold themselves into who they think their man wants. Maybe it would be more accurate to say you can't change a man.
I am not talking about only sex, ladies, though it is extremely important to be able to say no to sexual activities. He started dating you because of who you were without him. He must've seen something in you that he liked before you molded yourself into what you think he wants.
Relationships are about compromise - both of you. If he wants pizza again and you don't - say so. If he wants to see that scary movie and you absolutely don't - say so. Odds are, if he is asking you what you want, then he wants to know. I am no expert in men, but in my experience it is the woman that expects the "correct" answer not the man. Generally, I think, if he doesn't care, he won't ask.
What bothers me the most is clothing. I think it is a gross abuse of power when the man tells the woman what she can or cannot wear. I think this is the hardest time for a woman to say no. You want to look good for him. You want him to think you are pretty, but clothing is truly a personal expression. I am not talking about when you put on that top that shows all your cleavage to go to his parent's house. He says no, and, well, maybe you should change. But if you are wearing something appropriate and he just doesn't like it, say "No. This is what I am wearing."
You mustn't lose yourself in your relationship. You must be confident enough to say no and to hear it. There were a lot of problems with my marriage, but saying no was not one of them. I want to help you learn to say no. You are wonderful and beautiful and you do not need to change yourself for him.