Lack of sex drive

We just celebrated our 4 year wedding anniversary and 13 years together. We're only in our 30s and not trying to get pregnant. I want sex almost every night and he isn't into it or it takes a lot of convincing. I'm tired of always making the first move, but if i don't we don't have sex more than twice in 30 days. I feel like I have to beg for it or go frustrated. Any advice?