Tips for low libido?

So my partner and I have been together for 7 years and in the last few months our sex life has gone from 2-3 times a week to once every 1-2 weeks. We both work long hours and a lot of the time are totally wiped by the time we get to bed which I think adds to it. But, If I'm totally honest, I'm never really in the mood for sex anymore. We are still very happy together and regularly kiss/cuddle, but what can I do to increase my libido so that we can go back to having sex more regularly? I don't want to turn into one of those couples that never have sex! Xx