Welcome to HCM
Tel me about your self are you lactating mother or currently your are pregnant , what is your age now .
Bubble you felt in your breast are mammary glands so no need to panic but that bubble is larger then you must take opinion of gynaecologist in this respect .
may be due to mastitis
, or as a pregnancy
As your more anxious about these thing your heart beat increases . So 1 st confirm your diagnosis and take treatment for that disease because worrisome is not treatment of any disease it only worse that disease.