Period lasting for a month?

I'm 21 years old, found out I have pcos last year and irregular periods are VERY common with me ever since I first started. I'm freaking out a little, because this is the longest time I've had a period and it's scary. The longest period I've had before this lasted 2 weeks.. this time it came as usual.. stopped like it was suppose to, then 4 days later it started up again and that was 2 weeks ago.. and now it's very heavy and I'm cramping up a lot... :( has anyone else experienced this?