Cramping should I worry?

I’m currently 20 weeks and yesterday had intense period like cramping all day by my uterus, as well as back pain, no bleeding or any unusual discharge but it did feel uncomfortable. I was going to reach out to my ob today but I was no longer cramping although again tonight I feel slight cramping again with back pain. Should I be concerned? Anyone else experiencing or experience this? I have my anatomy scan this Friday.