Help! Cramping question

Hey guys. So when it comes to cramping, when is it recommended to call the dr? I have some moderate cramping, been on and off all day. Feels like I'm about to start my period but obv not going to bc I'm 28 weeks pregnant. I don't want to Google it bc every time I do that I freak myself out. Oh i should also add that i feel the cramping in my lower back. Mild but there. Baby is moving currently. Any help is welcome. Thank you.