Hey C.-
I'm going to be somewhat blunt, but that is the only way I really know how to communicate:
I agree with Amy. The main issue is that you and your husband are not on the same page when it comes to raising this child and your little boy senses it. Kids have an amazing ability to detect stress and strife in a home. It is a no-no to argue in general in front of kids, and it is especially bad for two parents to argue about the kids in front of the kids.
Your son is 5, and 5-year olds already push their limits as much as they can. Even in the most peaceful environments. They want independence. He is not only doing that, but he is craving attention from you guys. Ultimately, he wants positive attention, but subconsciously, he will take whatever kind of attention he can get...positive or negative. You both need to each spend one-on-one time with him and together doing things as a family to re-enforce to him that you love him and care about HIS world. Take just 10-15 minutes a day, each parent, playing a game with him by HIS rules...even if it doesn't make sense. It lets him know that he really IS important to both of you, just reaffirms things with him in such a small way.
You guys need marital help. Whether it be a doctor, pastor, counselor, all three, or more. It is hard to be in love with someone that you never agree with, but it also sounds like that you and your husband need some one-on-one time together like a weekly date night. I know that may sound really un-fun at the moment, but if you aren't spending stress-free fun time with each other, then yeah, you are definitely NOT going to be in love with each other! Find a relative or a sitter or drop-in care service for a couple hours once a week. Even if that means to re-arrange the work schedule somewhat. Your marriage is at stake here, and needs to be at the top of the list in rebuilding. Take some time for each other to get to know each other again. That can take you back to why you guys got together in the first place.
Yeah, it would would be a great idea to get into church together and put God at the center of your lives and your family. Those are the best places to start, but don't end there. Get help as a family. As a family, you need to completely exhaust every option with the goal of keeping the family together. Don't think about leaving until you really truly have tried all you really can do and there is a lot that you can do to make it work and have a peaceable and happy life as a family with a well-behaved child.
There are so many resources out there that can save marriages and family, wonderful things that are both Christian and non-church related. There is hope. It's worth it, for the welfare of your son and any future children in your home. I've heard the saying many times..."the best thing two parents can do for a child is for the child to see his parents love each other". There are other variations of that, but you get the idea.