Advice badly needed ?

Hi. I had my daughter at 23 weeks and now she's at home with us and 6 months old. (2 corrected) the last week I've notice that it felt like something imprinted in my uterus. And a couple days ago my uterus and vaginal hurt so bad and it felt like I had contractions again. Well tonight it felt like I had a small contractions again. But that shouldn't be since I'm pretty sure I'm not pregnant. So what could it be ?