Period back already?

Is it weird that I started bleeding again? I’m 6 weeks pp, the bleeding stopped around 3-4 weeks. I’m currently breastfeeding and got the depo shot around 4 weeks pp. For the past few days I have been bleeding and experiencing minor cramping. Is this because of my depo shot or has me period returned? I was under the impression that my period wouldn’t start until I stopped breast feeding. Also my 6 week check up is in a few days so I’ll ask my doctor but I wanted to know if any of you ladies experienced this before?