My mammo/us report was negative there were no suspicious findings but i do get pain in my left armpit. it says probable benign reactive lymph.imscared?

Wait: Benign reactive lymph nodes are exactly that; they are larger and tender because they are reacting to something else, like an infection elsewhere. With the negative mammogram and us, i would just do watchful waiting; if the pain/mass gets more painful or larger, or if it starts changing in appearance or feel, i would see the doctor again.