It you are experiencing excessive bleeding like this, you really need to be checked out by a gyno. Some of the time bleeding like this can be controlled by a birth control pill with lower hormone levels.
It is normal for your periods to fluxuate, and they may be heavier from time to time, but if you are bleeding too much you may begin to suffer from low iron levels (keep eating plenty of red meat!)
You are best to see your gyno, as only he or she can give you the tests required to see if this is having a detrimental effect on your health.
I hope that answers some of your questions.