Your husband sounds like he could have a chemical imbalance affecting his libido. My boyfriend had a huge drop in libido about five months after we started dating. It was horrible. I cried, I begged. I got rejected for sex over and over and over. I finally put my foot down and demanded he go to the doctor. It turned out that one of his vitamins and testosterone are both so low they're almost non-existent. Within a month of starting a vit regimen (prescription), his libido was back to normal. We never did the testosterone (dr suggested skipping it if vit therapy helped).
So, please consider getting your husband tested for anything that might hamper his libido - there might be some medicine that would restore your sex life!