Would go and see your GP and if they prove unhelpful I'd ask for a referral to a gynae or endocrinologist.
It could well be due to PCOS but you need proper medical advice first and foremost. You should have blood tests done to see what your hormone levels are like. Usually with PCOS there is an imbalance of LH (luteinising hormone) to FSH (follicle stimulation hormone) in that there's too much LH and not enough FSH.
They can also do an internal ultrasound scan to assess the state of your uterine cavity and ovaries (polycystic ovaries can appear larger than their normal walnut size and have multiple follicles on them. These follicles can and do disappear only to be replaced by further follicles).