hi.. you are having intermittent vaginal bleeding after taking progesterone
.. it is the common side effect.. but the periods will be painless.. because they are anovulatory.. sharp pain the left flank couldbe due to renal calculi
.. get one ultrasound examination done and see your urologist
for this... if the intermittent bleeding is disturbing you and causing anaemia.. see your gynaecologist to switch over to some other contraceptive
methods.. all the very best..