really bad mastitis or cancer??

i went to the doctor and she prescribed me antibiotics for mastitis, but they didn’t work so she called in another antibiotic and those haven’t worked either. i have a lump by my armpit, you can see it in the picture. my left breast is also very swollen, almost twice the size of my right breast.

it is very red and painful. i’ve heard that mastitis mimics some cancers in symptoms.... i’m worried, should i get a screening for the lump? has anyone else had breast cancer that was originally diagnosed as mastitis?