Help!

After having our LO 15 months ago, my sex drive is pretty much non existent. Is something wrong with me? I pretty much don't care for it. I haven't been the type to masturbate either.. I've only been with one person and we've been together for about 13 years. How would I go about increasing sex drive and spicing up our sex life. Also, who often initiates sex between you and your partner? Ideas on how to initiate sex? (He typically does).