Getting blackheads around breast line

I HAVE BEEN GETTING BLACKHEADS AROUND THE BREAST LINE AND ON UNDERNEATH THE BREAST AS WELL . IT IS A LOT OF THEM I START PICKING AT THEM AND SQUEEZING AS WELL THEY WOULD GO AWAY BUT THEN COME BACK AND NOW I HAVE THESE LITTLE DARK SPOTS FROM ME SQUEEING ALL THE TIME.AT FIRST I THOUGHT MAYBE MY BRA MAYBE TO TIGHT BUT I AM NOT SURE. SOMETIMES THEY ARE HARD AND PUS COME OUT. THEN I SAID MAYBE BECAUSE MY BREAST IN NOT THE BEST OF SHAPE THEY REALLY SAG I HAVE RIED EVERY BRA TO LIFT THEM UP. CAN YOU TELL ME SOMETHING HATE THE BLACKHEADS.