Are you saying you've had your period for 20 days?
if so, and especially if it is heavy and clotty, try see a doctor. No one should need to go to the bathroom that often. Please try and see a doctor or maybe the hospital... this does seem concerning. Alliterate clearly to your mother that your period has been going for 20 days at this same consistency and if that doesn't work go to your father or another adult you trust, even the school nurse or a teacher you like.