Partner with poor hygiene and zero sex drive

I’ve been with my current partner for just short of 4 years now, we have a 15 month old son and our sex life is...poor. And that’s putting it lightly.

It’s been nearly 6 whole months since we last had sex, he says its due to a low sex drive and external factors such as not feelings good about himself.

We the first 2 years of our relationship we were like bunnies, we always had sex, he always took care of himself hygiene-wise and now he’s the complete opposite, he will go months at a time without showering, cutting his nails, cleaning himself up and at first I was convinced it was depression but he is adamant he’s not and goes about day to day life perfectly fine, making time for anything he wants to do (gaming for hours usually) and I’ve offered to watch our son, run him a shower, have all his shower stuff out, prepared and I’ve gone as far as even offering to wash him if he really can’t be bothered.

Nothing seems to get through to him? About hygiene, our sex life and other things. I’m really trying and this relationship is on the brink of dying out, I’ve exhausted so many avenues, ways to be helpful, being harsher, being nicer, trying to help with stresses, taking nearly all financial burden, giving him more free time for things he likes and I’m still stuck here.

Can anyone give me any helpful advice? Has anyone been through this?