Hi, Im 33 Year Old Female Who Has PCOS My

Hi, im 33 year old female who has PCOS my last period was Dec of 99, well here we are 18 years later and i started bleeding /spotting 3 days ago, it has pretty much stopped now. My symptoms are, dark brownish spotting, nausea, heartburn, a couple headaches, light cramping. Im not sure if i could be pregnant since ive not had a period in 18 years, but last time i had sex was on 5/13 i started spotting on 5/25, its now the 28th and i spotted this morning but seem to have stopped. What are possible causes?