I am 21 and recently diagnosed with pcos. i haven't had a period in months and find when exercising i sometimes have spotting or minor bleeding. why?

Anovulation: If you have PCOS you aren't ovulating regularly, which can lead to irregular bleeding. The regular cycle of estrogen and progesterone that comes with ovulation is what gives you a regular menstrual period without bleeding in between. When you don't ovulate regularly it gets all screwed up in many ways. Check with your doctor as there are things that can be done to make it better.