Hey Emma

if you are BF it is unlikely to be the return of AF...

sometimes when the placenta is delivered, small parts of the placenta itself or the membranes may be retained in the uterus...if any small part was retained, as the uterus returns to its prepregnant size, it will try to expell these remnants.

are you getting any period like cramping with the spotting?
usually with retained products the bleeding is more noticeable during a BF

if the bleeding worsens or if you get a tempertaure or you are concerned make an appointment to see your Dr

hope this helps

xx yogababy