Period change after miscarriage?

We had our second miscarriage on Christmas Day. I started my first period about 22 days after I finished bleeding from the miscarriage. We waited a cycle before trying again as our doctor recommended. That first period ended on Friday, Jan 29th. So I put all my info into this app to find when we could try again. According to this app, which hasn't been wrong before, I should start my period next Friday . I started heavily today though,  aprox.21 days since my last period ended. So... I'm guessing my hormones are all whack now. Has this happened to anyone else? I've never had this little space between periods before, not even with my first MC.