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.
Shopping addiction
Shopping addiction is defined as the deficiency of impulse control which appears as the eagerness for constantly making new purchases of unnecessary or superfluous things. It is a concept similar to "compulsive buying disorder" and "oniomania", although these terms usually have a more clinical approach, related to a psychological individual disorder of impulse control. The phrase “shopping addiction” usually has a more psychosocial perspective . or it is placed among drug-free addictions like the addiction to gambling, Internet, or video-games.
: In this theoretical perspective, not incompatible with the previous approaches, shopping addiction is usually included among the so-called “drug-free addictions”, such as addiction to gambling and, specifically, within a number of addictions grouped together as social addictions such as the addiction to Internet, video-games or mobile-phones.
Diagnosis.
Since people buying more than they need is usual and accepted, even the most excessive behaviour takes a long time before being considered pathological. Shopping addiction generally manifests between 20–30