Im having a real hard time getting off cocaine and its a secret addiction

Im having a real hard time getting off cocaine and its a secret addiction. Reason is i have 2 kids and a loving bf all week long im home and its fine i work take care of the kids. BUT as soon as fri comes its like somthing in my brain clicks and im a moody b***h that cant think of anything but that first line... Thing is i dont understand why i can go all week not craving it then need it sooo bad. I need atleast 3-4 balls to satisfy my craving every fri i spend at least 900 dollars. After doing that much it takes 3 or 4 days for my noes to stop running and everyone feels bad for my "alergies" I have no mother and me and my bf dont talk about this i have been doing this for 9 years and im looking for words of encouragement or someones story that have been where i am and how they found the streath to stop...
                                                                            please help :(