low wbc (2.75) 7 weeks after radiaion only

Everything pertaining to low wbc mentions chemo. I need to her from others who did not take chemo please. Just lumpectomy then rads. I had a lumpectomy 3/2, and whole breast radiation 4/2 to 5/11. My counts where normal at the end of January. Now, July 2 everthing is normal expect for my wbc. Radiation office and primary doc says it cant be from radiation. Nurse at surgeons office says its not outside the relm of possibility. Which is it? My wbc usually runs in mid to high 3s. I am African-American and primary says that was not usual because I am AA. My wbc now is 2.75, low for me. She wants me to retest 1 week from the last test. Which makes no sense to me. What is one week going to do. Everything I read says low wbc will not come from radiating the breast because its not the big pelvis bone etc. I am worried. Seems to me the radiated my breast, right below my breast/rib area, and on my side/underarm. I had a huge dark block. I am actually hoping its the radiation and nothing worse!