Periods and drop injection after baby

hi, need advice. So my newes bundle of joy was born on the 27th may . I had my first period 8weeks later which is when I got the drop injection. I have had this befor and it usually stops my periods but i came on again about two and a half weeks after the first one and im still on now it's been over two weeks now. It's quite light but I'm concerned I know periods can get messed up after having a baby as this is my third but I've not had this before. Anyone else had this is it normal to come on again so quick and for so long even after the contraption injection?