spotting

so I’m on the depo and I go for another shot on September 13 and usually I start my period right before I go back to get my shot. I don’t have it for the two months and so I figured I would start it around September 1st since the shot makes my periods longer. I started having light spotting today and then it went away. Now I am having lower back pain and pain where my ovaries are. Is this my period coming?