nasty guy

Every time I'm with this guy he just always wanna do nasty stuff every time we're & sometimes I wanna do it sometimes I don't. He tries to make me the bad guy everytime I don't wanna do it. Just like this morning a few minutes I told him I was gonna suck his penis then I changed my mind because I didn't wanna do it anymore. He always wanna do something nasty when we are together. What should I do about this?