Pains but neg opk

Sophia • Mom of 2 🧒🏼👶🏽 Planned or accidental they are both a blessing from god 🙌🏽
I just posted before but I'm having cramps in lower abdomen and they are getting quiet sharp now I have like lower back pain but I've been testing all week and no positive opk or hpt first cycle after m/c but everything is back to normal doctors confirmed two weeks ago ? Anyone have any suggestions maybe AF ???