I have a shopping addiction.
Oh no!  The phrase shopping additiction usually has more of a psycho social perspective to it. 
I cannot go into a store without buying so much.
Oh I'm so sorry!  It's placed among other drug-free addictions like gambling, internet or video games.  What do you consider buying so much?
I go to the mall to find one cheap tank top and I leave with hundreds of dollars of clothes that I cannot afford, so I spend the next couple days stressing out trying to get money in my account to cover it before it cones through.
Sometimes that could be a Behavioral Addiction which is like a compulsion for a rewarding, non drug behavior - like a natural reward.  I'd say stay away from the mall!
Yes that is the best thing for me and online stores too!
Oh yeah online is bad bc it's 24/7!  There's a gene transcription factor known as FosB that's a common factor in additions!