The main abnormality here is a mild decrease in the neutrophil count- and it seems to have been present for at least 6 weeks...
It is unlikely this has anything to do with your headaches and breast pain- neither of these would be related to a mildly low white blood cell count.
A slightly low neutrophil count can sometimes be from medications- neither synthroid or premarin would do this, but is you are taking other vitamins or supplements, they may need to be considered.
It can be nutritional if you have certain vitamin or mineral deficiencies- particularly B12 or folate.
It can occur with certain infections- particularly viruses like EBV and CMV or HIV- but also certain infections like ehrlichia and ricketssia.
Finally it may be an 'autoimmune' condition or a bone marrow problem ( myelodysplasia) where you marrow just isn't making enough neutrophils.
Now again, your level is not in the dangerous level now- An absolute neutrophil count under 1.00 ( or 1000) is the point where you become more susceptible to a variety of bacterial infections. I would recommend follow up blood work again in a few weeks. And I would do some blood tests for a couple of the possibilities I noted above.
If it progresses and gets worse, and no diagnosis is made form the blood tests, then you may need a bone marrow biopsy- to directly sample the bone marrow. But again- I would stress there is no immediate medical emergency at these levels now.
Always ask if you need clarification/more information.
POSITIVE feedback & a BONUS are warmly appreciated.
Please note that answers are for information only, do not take the place of an assessment by your doctor,
and does not establish a patient-physician relationship.