Why wont my period go away?

ok so i usually have really heavy periods every month that are very painful not so painful that i cant walk but painful enough that i just crunch up in a ball with a heating pad if i were to take a bath with it it would literally be "blood bath" every now and then i get a light month and more then a breath of fresh air but its a pattern i make my calender to keep track the day it starts the day it ends. it goes like this: first 3 days heavy and painful next 2 significantly lighter not so painful but annoyingly painful off and on all day 5th day really light and is usually gone by the time i go to sleep or leaves sometime during the night. but as of the last 3 months its been so different 1 month heavy painful and all that jazz next month light not so painful next heavy ect but this month is by far the wierdest of the the 3 cuz it started out so light and no pain at all! i accepted it with open arms and thought of it as a catching a break that was on a sunday on tuesday it got a little heaver but not much still no pain thursday it got really heavy like it usually is but still wasnt painful so i was still grateful friday and sat it was light again then it got heavy sunday and monday and today tuesday i have to change every hr which i havent had to do for a while but i usually only have my period for 5-6 days never 10+days and i still dont have any pain! not that im complaining but my mom had cervical cancer and uteran cancer at age 19 im 17 she says she bled for 6 months straight so when i tell her whats goin on she just says its happened to her and its nothing but im worried this never happened before im not on birth control and i've never had sex i dont have a gyno doc at all and my reg doc is convinced that she knows best and whenever i ask for something she says "your young it has to be this way" so can anyone tell me whats goin on?