Bleeding when I shouldn't be???

I was put on birth control pills to stop bleeding. I was having 2 week or longer periods. I had my period while on the placebos and when I went back to the pill my period did not stop. About the 10day mark of bleeding it sort of stopped. I say sort of because I would wake up and have no bleeding for most of the day. I would take my pill about 1-2pm and then by 4-5pm I am bleeding with cramps. I feel like my birth control pill is doing the opposite of what it is supposed to be doing. What could be the reason for this? Do I need to call the dr? Should I stop taking the birth control pills?