5 months post bilateral breast reduction, having red areas that turn into pimples from one breast. Has happened 5 times (Photo)

I've had my breast reduction 5 months ago. Since then I've had redness and pain that eventually ends up coming to a head . It looks like a pimple and it starts to drain or I pop them. Yellow pus comes out. Sometimes it's thicker consistency (like popping a big pimple ). I have managed to heal them by keeping them clean and covered and using antibiotic polysporin. I am just curious as to what it is. Maybe old stitches? My plastic surgeon does not seem concerned. Wondering is it's normal?