Weird pulsing in lower back

Sarah • 22 ♍♎, 2 babies 💙Kaziah-James 04/19/16 &💖 Azariah 06/15/18

I'm having a weird pulsing feeling in the lower left part of my back, it doesn't hurt it's just pulsing. But not with my heartbeat. What could this be? And should I go to the ER??