I last had my period on the 10 jul had an hsg done on the 17 jul (i have pcos)no periods since .spotted once on the 21 aug, 18, 19, 20 of aug?

PCOS: Your delayed period has nothing to do with the HSG test. It is caused by the PCOS. With PCOS your body has plenty of eggs but has a difficult time achieving a mature follicle and then ovulating. The spotting you are having likely represents a thick lining that is breaking down and slowly leaking out. You should check a pregnancy test first. You may eventually need ovulation induction meds.