depo.

Okay so I started the depo shot back in October. Went to get my second shot (due to get it Jan 3) I was forgetful and didn't end up getting it untill Jan 21. I had started my period but figured after my shot it would go away. But I'm still bleeding. Has anyone else experienced something like this. I didn't bleed at all with my first shot and when on the shot back in high school I never blead ?