Thanks for asking. This is my therapy thread, so you may get way more info than you bargained for. I apologize in advance if my ruminations give you a headache! lol.
The short version is basically that our only real serious problems involved him being jealous on a couple occasions. All other problems were minor items that came up involving domestic issues and were resolved thru conversations.

Here's the long version for you if you are an insomniac or if you really want to know the nitty gritty of my sitch.
Your ? caused me to think carefully and the truth is that we rarely had disagreements, but rather discussions in which we would understand ea. other. I more deferred to or catered to his concerns than he to mine. (maybe I spoiled him). But I'm very easy going, so long as he kissed me hello goodbye and we did some fun stuff I was ok. He is very reasonable & practical so I often took his advice.
In 4 yrs., we had few problems. The worst trouble was when my exh resurfaced & would call multiple x a day. This was annoying to bf which was understandable. There was a point when xh wanted to meet me out for dinner. I agreed for various reasons. That's an entire other story. I knew I had no intention of reconciling, but I was intrigued and curious. I don't know how to explain how BF happened to drive by and see us dining at an outdoor table, but he did. He was immensely hurt and ANGRY. It was all very dramatic. By the time I reached home, he had already packed his things and was gone. I called him and asked for an opportunity to see him and talk to him about it. A week later, he agreed to listen to what I had to say. I still don't know how I ever persuaded him to trust me again, but he gave me the chance. It was very good communication, sincere apology, showing him the email I had already sent ex h telling him he was crossing boundarys and disrupting my r and that he must not contact me again, I admitted to a co-dependent behavior in the R w xh and asked for his support & understanding while I improved myself, etc. This was the only time I ever saw him break down and cry. Since I had not really done anything wrong, I think he could sense that was true. BF knew that I journal so he asked me to write to him about what love is. It was interesting homework and i learned a lot about love while I wrote to him. He was satisfied with my essay and we talked long about it. Following that I slowly built his trust step by step until we recovered from what was nearly a fatal blow. It's been 3 yrs since that, but now he admits he never really got over it and how the sight of the 2 of us sitting together still remains in his head & pains him. I can't undo that sight from his memory, but I never gave him reason to be concerned about it again. This created a scar that was hard for him to recover from. (I didn't take it lightly, although I thought he did blow it out of proportion, it's not like I had an affair. I am only just now realizing this was an indication that he could blow things way up, like with the cat.)
A few months later I spent mother's day with my DD father we went to a batmitzvah. He invited me last minute, I think to score a ride cuz I have a car & he doesn't. BF was working so I went. I sent bf a text that I was there. For reasons I don't understand he thought I lied about my whereabouts and was furious thinking I was seeing someone. He even called my DD father to verify my story! He said he was going to move out, but within a couple days I was able to calm him down and promised him I had the truth on my side. I guess this was a side effect of what had happened with my ex. This blew over and was never discussed again. He told me he wasn't going to worry about these kinds of things anymore because he'd seen an older couple walking hand in hand and decided that we would be like that couple, we were going to make it and he was going to stop worrying that I'd be untrue. Beyond that no further jealous behavior.

Our other problems were very small stuff. Like he talked to me once about he didn't like that I would wash clothes in the a.m. and then forget to dry them until the next day because he didn't like how the clothes smell after sitting wet overnight. I agreed that it wasn't a good habit and I didn't do that again.
He told me he didn't like that my DD would leave a mess in the kitchen. I mean if that kind of stuff is even valid as problems. They were, but not major issues. Other things like that - no fighting, just comments about ea. other's habits and a discussion which would result in more consideration.

Things changed after he was sick months on end. He was impossible. An instance was after Thanksgiving. We had spent it with his family. A few days later someone at work asked what I'd done for the holiday & I answered. Later BF was upset because he thought I told the customer that I'd spent the day with old people. He was so mad at that claiming I disrespected his family. He refused to admit he heard wrong. The comment doesn't even make sense since we are middle aged and the family gathering was of all ages. No matter how much I insisted he heard incorrectly he insisted he was right. Foolishness. This was the type of thing I began to experience with him. It caused me to believe that personality change and irratibility were symptoms of his mystery illness.

Maybe it's possible that he somehow began to associate me with the bad feelings he experienced with his illness. I believe my exh did this. He had hit a patch of unemployment that went on for months and he became so depressed. Once he landed a great job, he became involved with ow. I became the reminder of his bad period. So just now as I'm writing I realize that it's possible that there is a clue in this line of thinking. I know bf was becoming increasingly disappointed in what he thought of as my lack of concern or care for him in his illness.
The other day when we spoke he said I should have no trouble finding a man who can make me happier than he could. I told him I'm not even thinking about other men right now. But as I'm writing, there could be a missed clue in his words. He was making me so miserable while he was sick and perhaps it made him feel useless in the relationship, and he couldn't face the notion that he was responsible for my unhappiness, so he flipped it. If I didn't get the cat, it may well have been any other thing that gave him the excuse to flee and not feel like he was failing our r.

Ok, whew. There's some new angles to consider and some honest reflections. If nothing else, I hope all this agonizing will help me. Dang, I miss him. I'd take him sick or not right this minute. If only he were sitting next to me on his side of the sofa.... watching home improvement while I tap away on the laptop searching for shelter kitties on the interenet.