Hormones for sure. It was odd, I couldn't dredge up any desire at all. I could get off but it was like I couldn't be bothered, was starting from below zero instead of my usual +3, or the +5 of pregnancy, teenagehood, and 40s.
Nursing - i would get a strong feeling of doom when the milk came down, thought I was crazy and didn't tell anyone, found out many years later that it's called DMER and was not just some unique madness. But once it started it was fine, it feels about how you would imagine, physically. Emotionally, outside of the odd doom rush, it made me feel good about my boobs - they were very small even while nursing but made So Much Milk it made me realize they were real boobs, complete and functional, in a way I had not felt at all before.