What causes irregular periods?

I had a baby in July (my 3rd) and I’m not almost 3 months pp. I had my period twice so far but the second one ended a week agio and this morning I was bleeding again not a lot but still bright red and I wouldn’t say it was spotting either. It started bleeding again tonight. I haven’t ever had irregular periods but this just seems so odd. And now I’m freaking out and don’t know what to do and google is not helping. Anyone ever had this happen before? Is it hormones is it pid is it cervical cancer? Idk what to think I’m calling doctor in the am but I’m sure it will be a week or so until I can actually get an appointment. Any advice would be greatly appreciated