Extremely heavy period !!!!

I've always had a heavy, abnormal cycle but I'm needing some advice some others who may have gone through this. I have PCOS and recently started taking 500 mg of metformin daily for it. This is my first period since starting metformin and it is so painful. I'm bleeding through super plus tampons in an hour or less with a super plus overnight pad under it. My friend suggested I try the diva cup because it holds more. I filled it (15ml) and then some (it leaked over the top) in about two hours. I feel terrible and had to miss work today. I'm not sure at what point I need to be checked for something else or if there is a point that I'm bleeding too much. Anyone have any advice ?