Falling out of love

I don’t know where to start, I’ve been with my bf for 12 years we have a 5yo together. We were trying for baby #2. But Lately my hearts just not in it anymore. I’ve fallen out of love with him. It happened gradually within the last 4 months. And today while he was trying to be romantic it just hit me- I have no romantic feelings for him anymore. It’s sucks but nothing’s there like that anymore. I don’t want to break up our family, but I want out. I don’t know what to do.