Excessive Bleeding...

i have 3 children n after every child was different
first child i bled for a few weeks then everything stopped n i went straight back to my 28 day cycle
2nd child i bled for 6 weeks before finding out i had an infection n needed antibitocs n a curet after that i pretty much stopped bleeding straight away
3nd child (this one) i bled for a few weeks then spotted for about a week stopped bleeding for like 2 days bled for a day (which my doc thinks was a period) stopped for another 3 n now ive been heavily bleeding again for like 2 weeks...might i add its so heavy i have to change my pad every hour without fail cause if i dont i bleed out the sides, front n back and im wearing nighttime pads i shouldnt be leaking in an hour....i feel heaps run down as my iron levels were measured at 4 about 6 months ago n i hate to think what they r at now
i see my doctor tomorrow again though so maybe he can help??
what do u guys think is it normal to bleed so much