Hello Anchy,
It is always helpful to know the details of the dream...the more detail that you include, the better probability of accuracy from my end. Sometimes it is difficult to remember the specifics I know. Even without specifics important aspects can be gleaned.
To shop in ones dream shows often indicates that the dreamer has something to decide or looking to fulfill a need (especially since this dream is a repeating theme for you). So during the period of the time you had these dreams you were likely searching for answers, or looking to "buy into" a concept or idea. In the dream, if you had actually made a selection and then purchased you have likely made a decision. If you feel that your forgetfulness dream was directly associated to the decision and purchase dream, then it is possible that you have not followed that which you have decided upon.
Example... I once worked with a dreamer who had similar theme dreams. Like yours, they were presented back to back over a short period of time. In her dream she was shopping for a book that would help her to understand and implement a better nutritional lifestyle and she was pleasantly surprised when she found just what she was looking for. She left the store but she also left her book, her wallet, and her purse. She went across the street to a cafe and had a very expensive lunch that she knew was bad for her health. When she could not pay for the lunch (because she left her stuff across at the bookstore she asked the manager to allow her to leave to get everything she had forgotten at the bookstore.
She went to the bookstore and retrieved her wallet, and purse but she could not remember what she had bought.
IN essence she had made a decision, and a commitment, (buying in to the idea to do the right thing) but she did not follow through because she went across the street ( back to the old ways) and forgot about it.
IN reality she admitted that this is indeed what happened. She planned the perfect diet and new way of life but she soon fell off the wagon, (forgetting her commitment).
In some parallel way, it is likely that you have also forgotten about a commitment or have not followed through?
regards,
sailrmc