Romance Satisfaction gets low very quickly

 Hi, in my game, the pink bar of my Sims decreases very quickly. Within hours or a day, the bar turns grey again and then red. It's almost impossible to have a child or get married, because by then the bar is grey again, as if they didn't know each other and I have to start from scratch again. In addition, my Sims' fear of being left by their partner doesn't go away. I've already tried removing all mods, but that didn't help. Can anyone help me?