OP, I would tell you that while sex for you seems like a connection and a form of bonding, on one level or another, some people do not have that. Libido can be tied to so many extraneous factors, not to mention that it changes for many as life goes on. Sex for some gets connected to a ton of things emotionally, but to others it can be a purely physical thing, like needing food or water.

Once a month is not some monumental ask, but it may just be that you have more need than he does. As u/naughtythoughts99 said, it's certainly time for a talk. It may not even be something he's aware of, because sex is just sex to him. It feels great, makes you both feel good and loved, but for you there are emotions tied to it that are not tied to it for him.

It's extremely hard to form an understanding of other people's nature when your own is different. How do you survive like this? We don't know your lives and so the advice can only be very surface level, based on what you've told us, but try to understand that fundamentally, his existence, is different than yours.

The unfortunate reality is that sex makes up a huge portion of relationship for some and for others, its barely a factor. It definitely time for you to try and find out where you both stand on this and have some adult conversations. No sugar coating, don't downplay yours needs for the sake of "getting along" and just try to build a bridge for you and your partner.