Belly just got really soft & not pregnant feeling

I’m 19 weeks and whenever I lay down for the past month and a half I’ve been able to feel my uterus/my belly has been slightly hard. Just now, it got really soft and felt like it did before I was ever pregnant!! I couldn’t feel my uterus anywhere. I was just feeling kicks and her pushing her butt up then it all disappeared lol. Is this normal?? Has it happened to any of you?