Is It Normal To Have Menstrual Bleeding For 15 Days?

HI, I am 29 year old been diagnosed of PCOS. my periods have become very irregular for past year. They happen every month for like 15 days or so. I also gained a lot of weight so I am trying to loose weight now,but this month i still have irregular vaginal bleeding for 15 days...its bright red in mornings and by end of day it gets light pinkish..i dont need a pad for this. What should i do? doctor told me to get on metformin but i want to control my cycle by weight loss...is it okay to bleed like this for next few months without taking medication?