Low Iron Levels. History Of Hysterectomy. Reason?

Hi Doctor Samuel, my name is Lynda I am 47years old. I have over the last year dropped in my iron levels to a very low level. I am told normal is 20 - 200 and I have gone from 15 to 14, 11 and now 9. I am vegetarian and have been for last 6 years so nothing has changed. I had a hysterectomy at 34 so it is not due to monthly bleeding . Can you advise me what may be going on in my body to have dropped so low. The above figures are from blood tests taken every 3 months for the last year. Thank you, Lynda