What is Happening with my Body? Fever and Sick After Breast Reconstruction?

Low-grade fever with high leukocyte count are concerning and indicate possible infection. You should closely follow-up with your plastic surgeon and look out for any swelling, pain, and/or redness of the breasts.

I am hopeful your symptoms have subsided by now with treatment.  There are many unanswered questions in your question but you have to trust your doctor to do the best thing for you and hopefully your surgeon is doing that. 

Tissue expander, fever, not feeling well, high white cell count?? It is infection till proven otherwise. Tissue expander needs to come out and antibiotics by vein after cultures are taken.