Maybe my story will provide a little reference and hopefully be of assistance.....
Married for almost 20 years, with two teenagers. Without question, my marriage has never been better, and my wife would tell you the same.
As recently as two years ago, we were both independently - ie, without each other's knowledge - looking into divorce. We each went so far as to contact divorce attorneys. There is a lot that I could go into and understand that we both did very hurtful things to each other, but I'll spare you the details. But if I could boil it all down to one thing, it was communication. We simply didn't communicate. We were two people who happened to have kids together who were sharing a house.
Over time, that lack of communication, of sharing, led to resentment. We resented each other. I used to have terrific arguments with her...all in my head. We never really fought, either. Neither of us wanted conflict, so we just did our thing, stayed out of each other's way, and tried to get along. We actually got along fine, but there was no passion, no love, no selflessness. It's very sad to think back on what all we missed out on.
Her affair was the real catalyst for change. While I didn't have an affair, I also did some very, very destructive things. I created a toxic environment in which an affair could happen. No, I'm not naive. She made a conscious choice to have the affair and nobody forced her.
So what did we do? We made a commitment to save our marriage. We learned to talk. REALLY, really talk. We turned off the TV, put down our smartphones and laptops, and talked. We had many, many difficult and painful discussions. We were brutally honest with each other. We also decided that we needed help. We each saw therapists. After a while, we started seeing a marriage counselor, and it was very helpful.
IMO, you should sit down with your husband and have a very frank and honest discussion. Don't do this in bed late at night. Don't do this after you and husband have had a couple drinks. Be loving but firm. Tell him that you are worried about your marriage and you want to do whatever it takes to make it work, to make it better. Don't produce a list of things that he does that you don't like (that's nagging), but paint a picture of what your marriage can be. Tell him that you will fight for him.
Maybe he won't agree that it needs work, or maybe he won't agree to do the work. You can't make him.
Best wishes to you!
Rookie Scribe