Since you have got PCOS, plus have started on the depo, i would say its just one of them horrible side effects of that. Sometimes my cycle can be just as you have described. As of now, i haven’t had a period for 5 months yet i am on no contraception or medication to cause lack of periods. But i can guarantee when it comes it will be just like yours! But hopefully you get to the bottom of it soon, hopefully they can give you something to help slow it down or make it stop. I will say i had awful side effects when i was on the depo injection, but then again any form of contraception doesn’t agree with my body either! Good luck with your appointment! Let us know how you get on.