Spotting?

My period is supposed to start today but the past couple of days I’ve had light blood and it was pink. He first day it started, there was some brown. I thought I started my period but then it went away. A keeps going away and coming back but only lightly and it’s pink. It was a little dark today but not much. My lower back has been hurting on and off and my stomach has been too. This hasn’t ever happened to me (I have 3 kids) and idk what’s going on if someone could please let me know what they think. Thank you.