Well, if your testosterone levels are out of whack, which they most likely are if you have PCOS, yasmin or yaz will lower those levels (yaz is stronger than yasmin). I've been on metformin with the yasmin for about 2 months and I'm already feeling better
I also have a friend who would bleed HEAVILY for days on end and ended up in the hospital from too much blood loss. She was diagnosed with PCOS and was put on metformin and the pill (not sure which one, probably yasmin or yaz) and the bleeding subsided. She also lost 40 pounds as of the last time I saw her and the thinning of her hair had started to go away...so hang in there! It's most likely your testosterone levels that are causing your problems. Once you figure that out and get them back to normal your extreme bleeding will probably subside!