What is this pain?? 😩

I will be 31 weeks tomorrow. I woke up this morning with back pain and what feels like bad period cramps. I called labor and delivery and they told me to get checked because I have high blood pressure. I got there and sure enough my BP was high. They hooked me up to monitors but I wasn’t contracting. I was released after being treated for my high BP. My question is, what is this pain? It has been consistent since around 7am. They checked my cervix. It is still closed and baby is still high.