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How long have you had the card, and how long have you been using it this way?
In any event the Chase card is not the best card for buying from Amazon. You would generate more rewards with the Citi Forward card which awards 5 points per dollar on purchases from bookstores (including everything purchased from Amazon), music stores (including iTunes), restaurants, and cinema tickets.
While forward is 5 points there is a 75k point cap per year, 15k purchases so would be exhausted very quickly if OP spends 20k month.
I would suggest either asking for a cli or opening a new card with a bonus and then reallocating the limit from new card to old card after getting bonus if you want to save your inq's