You're certainly not the first couple to deal with this scenario, and part of what you're describing sounds like a totally normal pattern. In relationships, what usually happens is there's a burst of sexual activity in the early days, and then as time goes on, sex becomes less frequent. That's not to say people in long term relationships can't or don't have satisfying sex lives, but that some of what's going on here is a common progression.
Beyond that, can you give me a sense of how much you and your partner have talked about this mismatch? I don't mean just in terms of you trying to initiate sex and her saying "no." Have you talked about what's going on, and how you're each feeling about it? If you haven't, this article has some great advice about approaching that conversation: https://www.scarleteen.com/article/advi ... o_more_sex
Too, when you say you miss being intimate, have things like more general physical touch (kissing, cuddling, etc) gone away as well? Or is it mainly sex?