What Causes Excessive Bleeding During Beginning Of Periods?

For about 30 hours near the beginning of my period, I have to change a super plus tampon every 50-60 mins unless I put 2 in, side by side giving up to 2 hours. I always wear a pad too, as 90 mins isn t long. However, the flow tails right down to normal heavy for the next 24hours, then practically disappears. I m healthy, eat a varied diet, exercise and have a low bmi. It s annoying and has been like it for a number of years now. Should I see a doctor? No cramps generally anymore.