My shoulder blades where in agony so i did what I usually do and lean back and do a sharp twist with My upper body to crack my back I haven't don't it since being pregnant as i didnt have this upper back pain until today when I did the sharp twist i felt a sharp pain at my lower belly above the pubic area it was only one sharp pain and doesn't hurt now I'm worried because my friend said I couldn't ripped the placenta will it be OK how will I know if anything is wrong? This is My first pregnancy I don't want anything to happen to my baby I'm nearly 16 weeks