Help me

Okay so basically I’ve been taking birth control since I was in 7th grade and I’ve been switched by my doctor 2 times since I’ve first started . I’m about to be 17 and still having extremely irregular periods . Irregular to the point as to where they last up to 17-20 days usually and if not then I get 2-3 periods per month. My cramps are so extremely bad that it hurts me to the point as to where I want to vomit and my legs will not move. I’m not sexually active . I take my birth control on time everyday . I am worried I may have pcos does anyone have anything similar that has ever or is currently happening to them ? My periods are also EXTREMELY heavy to the point to where I go through 6-8 super+ tampons daily on my period.