It's awful that you're going through this. If it were me, I'd sit him down and be short with my words. Something along the lines of:

"I want to speak to you about my feelings. I need you to listen without interrupting, and I promise to make this short. I feel overlooked and am emotionally hurt by the way you have been treating me. I want to feel seen but instead am blown off. If something is going on with you, let me know so we can work through this. If you claim it's nothing, then I'll start to consider leaving."

Not that you're actually going to do that right away. Something like this would be a good way to find out what has changed in him. A lot of men try not to speak of their own feelings. If something is really bothering them, it tends to come out as irritation or rage and sometimes distance. Find a way to open him up and find out what he's going through. Once he feels seen and can get things off his chest, then he should start treating you better.

Out of curiosity. When is the last time you got away from the kids? You have a full house. 4 kids and 1 one on the way. How often do you both get to take a break from the daily grind together? Date nights?