you may have endometriosis
, you said you have PCOS
. in PCOS irregular peroids are very common because this is a condition of male sex hormone excess. mainly occurs due to LH hormone and altered Insulin
sensitiveness. please consult your gynaecologist. because period regularization and modifying insulin sensitiveness is mainstay of treatment. ultrasound
or MRI can give you a clue of proper diagnosis. anyway your present symptoms does not match any cancer.