Decrease in sex drive

Hey ladies,

My husband and I have been together for four years, and married for two. We are both really busy and work opposite schedules so we only get to spend time together on the weekends. Over time our sex life has slowly decreased, and now usually only happens once a week on the weekends, but sometimes it seems like more of a chore (although it's worth it ) it makes it hard to get in the mood. I feel like we have lost our passion. It did pick up a bit when we first started ttc, but has dwindled back down. Has anyone else experienced this? If so, how did you get your passion for each other back?