Any chance you got your tubes tied with your son? Blood hormone levels stay the same... but sudden loss of sex drive (until menopause or reversal) is a common side effect (along with mood swings, personality shift, lubrication issues, smell issues, irritability, pain sensitivity, etc.). It's still being studied as to why that's 'possible', although from last I read the anectdotal has finally shifted to a strong correlation was already shown (these studies are ongoing).
The 3 biggest libido killers are (in order)
- tiredness
- hormones
- depression
If your hormone levels are good (and you didn't have a tubal)... how about the other 2?
A less common cause is smell. It's something patients with certain kinds of cancer have to cope with when they lose their sense of smell, and it's a common "speed bump" in many relationships/ marriages. Our brain ties certain emotional and physiological responses to smell. If your spouse usually wears a certain cologne (or deodorant/ aftershave/ etc.), and stops or switches... or even if you just start washing everything in different detergent... it can mess with your brain 'recognizing' the vavoom in your husband. Your MIND knows it's him, but your brain is lacking a road sign. A lot of people change EVERYTHING when a baby is born (stop buying the expensive cologne, switch to unscented everything, etc.). This is a quick and easy fix if y'all changed things up a few years back. It's a harder fix if something hormonally has shifted in HIM (changing his smell), or if you guys radically changed your diets, or if he has any health problems (like tooth decay, halitosis, etc.) that changed his smell.
Anyhow... just a few thoughts/ avenues to explore.