What Is The Cause Of Heavy Bleeding?

When I am on my period, my sleep is disrupted by it because I have to change sanitary protection at least a few times a night and when I wake up I see dry blood on my inner thighs and on my bed sheet. Both day and night, I have to wear a tampon and a pad. I sometimes have to throw away my underwear because of the blood stains left over even after washing the underwear. Should I be concerned?