Once you have started HRT as you have - it is difficult to say whether any bleeding is due to your own cycle or due to the HRT, although signs should indicate whether you've had an oestrogen surge! I don't think you can start counting again from your bleed, but it could be your own cycle. You asked about a scan - I would suggest you have a scan immediately following your bleed - which would determine its thickness and hopefully any problems or pathology , but not necessarily whether it is due to your own cycle or hormones breaking through?
Hurdity x