how do I make him want me?

I've been with my boyfriend for over a year, we have known each other since we were kids about 5 or 6. okay so the issue is this, when we got together over a year ago, we used to have sex more than twice a week. And now, we have maybe once a week if not 3 times a month.. no matter how much I try to have sex with him, he never wants sex. I even tried talking to him about it, and he says sex isn't important. he doesn't try to have sex either... . what else can I do for him to want me?