There is a huge variation in how frequently people want to have sex. Some couples enjoy sex every day. Others are happy having sex once a month.
Your age, stage of life and current circumstances can all impact on libido. Many couples have a discrepancy between their levels of interest in sex and there is frequently a discrepancy between how often people want sex and how often they actually have it.
An important factor to consider is: are you and your partner happy with the quantity and quality of your lovemaking? If there's a big gap between your levels of interest and this causes serious conflict or tension in your relationship, this would be a good reason to seek sex therapy.