Do you need more sex, or do you need more sex from him? This is an important difference that will change my whole answer.
You need more sex from him, but he doesn’t listen. Do you know the cause? I can think of two possible reasons. 1: He’s not really into you. Why could this be? Are there other reasons he might be in a relationship with you? 2: His libido isn’t as high as yours. Have you talked with him about either of these two reasons?
I think there are two possible solutions depending on how you answered my first question. If you want him to be more active, figure out what’s holding him back. From there you can figure out your differences and grow together. I have no idea what problem he might have, maybe it’s even as simple as a lack of confidence. Counseling might help here. If you simply want to be more active yourself, opening the relationship might help. I’ve been in open relationships and am currently in a half-open one. Despite it being uncommon it can be a good solution based on my own experience.