Depo Shot Issues?

I got my depo shot last month and per usual it was done on the 5th day of my period. The doctor who did it told me that my period would finish regularly and then probably wouldn't come around again except for some light spotting ( left overs ) but since I got the shot I have not stopped bleeding. And it isn't heavy like a period but it is to the point that I had to wear a liner or two every single day because it was ruining my panties. Has anyone else had this issue? Or know what to do about it?